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Species and Incompatibility Determination within the P1par Family of Plasmid Partition Elements

Gene Regulation and Chromosome Biology Laboratory, National Cancer Institute, CCR, NCI-Frederick, Frederick, Maryland 21702-1201

Received 25 March 2005/ Accepted 10 June 2005

	ABSTRACT

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The P1par family of active plasmid partition systems consists of at least six members, broadly distributed in a variety of plasmid types and bacterial genera. Each encodes two Par proteins and contains a cis-acting parS site. Individual par systems can show distinct species specificities; the proteins from one type cannot function with the parS site of another. P1par-versus-P7par specificity resides within two hexamer BoxB repeats encoded by parS that contact the ParB protein near the carboxy terminus. Here, we examine the species specificity differences between Yersinia pestis pMT1parS and Escherichia coli P1 and P7parS. pMT1parS site specificity could be altered to that of either P1 or P7 by point mutation changes in the BoxB repeats. Just one base change in a single BoxB repeat sometimes sufficed. The BoxB sequence appears to be able to adopt a number of forms that define exclusive interactions with different ParB species. The looped parS structure may facilitate this repertoire of interaction specificities. Different P1par family members have different partition-mediated incompatibility specificities. This property defines whether two related plasmids can coexist in the same cell and is important in promoting the evolution of new plasmid species. BoxB sequence changes that switch species specificity between P1, P7, and pMT1 species switched partition-mediated plasmid incompatibility in concert. Thus, there is a direct mechanistic link between species specificity and partition-mediated incompatibility, and the BoxB-ParB interaction can be regarded as a special mechanism for facilitating plasmid evolution.

	INTRODUCTION

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Low-copy-number bacterial plasmids contain active plasmid partition systems that move plasmid copies into daughter cells to ensure that each cell receives at least one copy after cell division. In each case studied so far, the system consists of a single locus containing an operon for two proteins and a cis-acting partition site. The first protein is an ATPase, and the second is a specific DNA binding protein that recognizes the cis-acting site (29). Related systems can be found on the chromosomes of a variety of bacterial species, where they are implicated in chromosome segregation (13).

Partitioning systems can be divided into two types: one encoding an ATPase of the Walker-type ATPase superfamily (18) and the other an actin/hsp70 type ATPase (3). The Walker-type systems are common and widely distributed among plasmid species. They can be classified into two groups, designated types Ia and Ib (13). Type Ia is the best characterized and includes the intensively studied partition systems of the P1 and F plasmids of Escherichia coli (P1par and Fsop). Although the F and P1 systems show some homology, they have cis-acting sites with very different organizations. The F site (incD) consists of 12 contiguous 48-bp repeat sequences just downstream of sopB, the second partition protein open reading frame (17). The P1 partition site, parS, is similarly placed downstream of the parB open reading frame but consists of a single copy of a sequence approximately 80 bp long. Within it is a central integration host factor (IHF) binding site flanked by two ParB binding regions (7, 11). This type of site is characteristic of a distinct family of partition systems, the P1par family, found in a variety of plasmids from various gram-negative bacteria (12).

Three members of the P1par family have been studied extensively. The P1 and P7 systems are from closely related bacteriophages that have plasmid prophage forms (1, 22). The pMT1par system is from the large virulence plasmid pMT1 of Yersinia pestis, the facultative intracellular agent of bubonic plague (9, 21). Despite the fact that these three systems are very similar in terms of sequence and organization, each shows a unique species specificity. The parS site of one species is unable to function using the Par proteins of another species (27). This specificity is speculated to be an advantage in preventing competition from other family members (2, 24).

In the case of the P1 and P7 par systems, the critical information for species specificity has been mapped. It resides in a pair of direct six-base repeats in parS (the BoxB sequences), and in a short motif within the C-terminal domain of the ParB protein termed the discriminator recognition sequence (DRS) (25). These sequences recognize each other in a species-specific interaction (15, 24, 25). The localized contact between parS BoxB and ParB is distinct and separable from the binding contact between the parS site and the protein that provides the bulk of the binding energy (28). The latter involves a different set of parS motifs, i.e., the BoxA sequences, which bind to a helix-turn-helix motif in the interior of the ParB sequence (25, 28).

We have speculated that the BoxB-ParB contact might constitute a special mechanism for defining species specificity in the P1par family. This idea receives support from the properties of pWR100par from the recently characterized large virulence plasmid pWR100 of Shigella flexneri (27). There are many sequence and organizational differences between the parS sites and the ParB proteins of pWR100 and P1. However, the BoxB sequences and the ParB DRS motif with which the boxes are thought to interact are very similar. As predicted, the pWR100 and P1par systems show identical species specificities (27). Here, we show that the unique species specificity of the pMT1par system is determined by a unique variation in the BoxB repeats.

Plasmids of similar types exhibit incompatibility: they cannot be maintained together in the same cell. Partition systems are a major factor in determining this (2). Two plasmids with identical parS sites compete with each other for partition, leading to the loss of one plasmid or the other (2). Most P1par family members have unique incompatibility specificities: they interfere only with their own types. Here, we examine the incompatibility specificities of parS sites with altered BoxB sequences and show that species and incompatibility specificities switch in concert.

	MATERIALS AND METHODS

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Media, enzymes, and materials. Bacterial strains were grown at 37°C in LB broth (26) unless otherwise stated. The following antibiotics were added to media at the indicated concentrations unless otherwise indicated: ampicillin, 100 µg/ml; chloramphenicol, 10 µg/ml; tetracycline, 6.5 µg/ml; and kanamycin, 40 µg/ml. Restriction endonucleases were obtained from New England Biolabs (Beverly, MA), Gibco-BRL (Gaithersburg, MD), or Boehringer Mannheim Biochemicals (Indianapolis, Ind.). T4 DNA ligase, DNA polymerase, and the Klenow fragment of DNA polymerase I were supplied by Roche Molecular Biochemicals (Indianapolis, IN). QuikChange multiple- and single-site-directed mutagenesis kits and XL10-Gold Kan^r competent cells were obtained from Stratagene (La Jolla, CA).

Bacterial strains and bacteriophages. Strain CC4247, which is a argF-lacZ U169 derivative of W3110 (20), was used for chromosomal integration of the plasmid par genes. DHB6521 (5) was used as a lysogenic strain for InCh1. Strain M1967 is MG1655 zwf<>kan. It has the kanamycin resistance gene of Tn5 substituting for the deleted complete open reading frame of the zwf gene. Bacteriophage cI₈₅₇-P1:5R1005 was maintained on strain YMC (15). Partition tests used strains CC4902, CC4913, and CC4916, whose chromosomes contain single copies of the P1, P7, and pMT1par genes, respectively.

Strain CC4902 has the P1par operon integrated at att expressed constitutively from an attenuated plac promoter (20). The P1par genes were integrated using the InCh method (5). The strain has a single P1par operon, a selectable bla gene, and a hybrid att site (20). Strains CC4913 and CC4916 are similar to CC4902 but contain the par operons of P7 and pMT1, respectively. Plasmids pALA2905 and pALA2906 were the sources of the integrated DNA. The genetic structure of the insertions was confirmed by PCR analysis. Each construct contains a single copy of the appropriate plasmid's par region under the control of an attenuated, constitutively expressed plac promoter.

Plasmids. Plasmids pALA1901 and pALA1931 have been described previously (14). Plasmids pALA1413, pALA1414, and pALA1846 are derivatives of pBR322 that carry the P1, P7, and pMT1parA-parB operons, respectively (24). Plasmid pALA2466 was constructed from pDSW210 (30) and has a cloned PCR product from pALA1413 (20) by use of the following primers: 5'-CCGGAATTCAGTGAAATTCCAGCCAGCTT and 5'-GAGGAAGCCCTTACTCCTCAGTTAGATCTGA. The parA and parB genes were inserted between EcoRI and HindIII sites, deleting the gfp gene of the vector. This insertion changes the N terminus of ParA from Met Ser to Met Glu Phe Ser and places the par operon under the control of an attenuated lac promoter.

Plasmid pALA2900 was derived from pALA2466 by the deletion of lacI^q by BssHII digestion and religation. Plasmid pDSW210 (30) was digested with MluI and NarI, and the ends were filled in by Klenow enzyme and ligated to give pALA2908. The EcoRI-to-HindIII fragment of pALA2908 was then replaced with a PCR product containing the P7par region from linearized pALA1414 to give pALA2905. The primers were 5'-CGTCTTCAAGAATTCCCGCCATTTCTTTA and 5'-CATTAAAGCTTCTAGAGAGCTTTTTTCAT. A PCR fragment carrying the pMT1par genes was produced from pALA1846 with an XbaI extension at the left and a HindIII extension at the right end. This was inserted between the XbaI/HindIII sites of pALA2908 to produce plasmid pALA2906. The primers were as follows: 5'-GGATCCTCTAGATACAAAATATGTTGTACA and 5'-CAGCCAAGCTTCCTTATCCCTTACTCACCTG. The par-deleted lambda-mini-P1 plasmid c1₈₅₇-P1:5R1005 and plasmids pALA1952, pALA1993, and pALA1843 were as previously described (24). On recombination, they gave rise to -P1:5R1005::pALA1952, -P1:5R1005::pALA1993, and -P1:5R1005::pALA1843 (31).

Plasmids with hybrid parS sites were obtained by multiple- and single-site-directed mutagenesis of the P1, P7, and pMT1parS plasmids pALA1952, pALA1993, and pALA1843. The mutagenic primers that introduced point mutations into both B boxes of the parS sites were as follows: (i) 5'-CCTTTTTTGTATGTTTTTCGCCACGCCAATTTCATGG (places a P1 base in pMT1 BoxB1) and 5'-CTTTCACACTGAAATCGCCACGCTTTTCAACCTC (places a P1 base in pMT1 BoxB2), (ii) 5'-CCTTTTTTGTATGTTTTGTCCCACGCCAATTTCATGG (places P7 bases in pMT1 BoxB1) and 5'-CTTTCACACTGAAATTCCCACGCTTTTCAACCTC (places P7 bases in pMT1 BoxB2), (iii) 5'-CCGGATCCAAACTTTCACCATTCAAATTTCAC (places a pMT1 base in P1 BoxB1) and 5'-CAAGGTGAAATCACCACGATTTCACCTTGG (places a pMT1 base in P1 BoxB2), and (iv) 5'-CCGGATCCTAAAATTCACCGCGCCTATTTCATG (places pMT1 bases in P7 BoxB1) and 5'-CAGGCTGAAATCACCACGGTTTCACGCCTG (places pMT1 bases in P7 BoxB2).

The following pairs of primers were used to introduce changes in a single BoxB: (i) 5'-AATAAGTGTCCGGATCCAAACTTTCACCATTCAAATTTCACTATTAAC and 5'-GTTAATAGTGAAATTTGAATGGTGAAAGTTTGGATCCGGACACTTATT (places a P1 base in pMT1parS BoxB1), (ii) 5'-CTCTAAAATTTCAAGGTGAAATCACCACGATTTCACCTTGGATCG and 5'-CGATCCAAGGTGAAATCGTGGTGATTTCACCTTGAAATTTTAGAG (places a P1 base in pMT1parS BoxB2), and (iii) 5'-CCTTTTTTGTATGTTTTTCGCCACGCCAATTTCATGG and 5'-CCATGAAATTGGCGTGGCGAAAAACATACAAAAAAGG (places a pMT1 base in P1parS BoxB1).

The primers were annealed to the template plasmid, digested with DpnI, and transformed into XL10-Gold competent cells (Stratagene). The DNA sequences of the mutant plasmids were determined. The resulting plasmids were recombined with c1₈₅₇-P1:5R1005 and used in partition tests as previously described (20).

Plasmids pALA2920, pALA2921, and pALA2922 are derivatives of pACYC184 carrying the P1parS, P7parS, and pMT1parS sites, respectively. They were derived from pALA1849, pALA1850, and pALA1851 (31) by having the tet gene replaced by a kan (kanamycin resistance) cassette. The kan cassette was amplified from strain M1967 genomic DNA (a gift from Lynn Thomason), using primers 5'-GCTTATCATCGATAAGCTTTATGGACAGCAAGCGAACCG and 5'-CGCCGAAACAAGCGCTCATGATCAGAAGAACTCGTCAAGAAGto give a fragment with HindIII and BspHI extensions. This was placed between HindIII and BspHI sites of pALA1849 and pALA1851 to give pALA2920 and pALA2922, respectively. To obtain pALA2921, the kan cassette was recombined with pALA1850 to replace part of the tet gene with kan by red-promoted recombination (32). The recombining fragment was produced by amplification of the kan cassette using the primers 5'-CTTATCATCGATAAGCTTTATGGACAGCAAGCGAACCG and 5'-CCGAAACAAGCGCTCATGATCAGAAGAACTCGTCAAG.

DNA procedures. Plasmid DNA purification, DNA sequencing analysis, oligonucleotide preparation, and other DNA techniques were carried out as previously described (25).

Incompatibility tests. Incompatibility tests were carried out essentially as previously described (31). The retention of the pACYC 184 derivatives throughout the growth of the strains on the plates was ensured by 30 µg/ml of kanamycin.

Partition tests. Each parS site was tested as a -P1 miniplasmid construct (-P1:5R1005::pALA1952, etc.) using the pickup partition assay (15). The constructs were introduced by infection into a strain supplying the relevant Par proteins in trans. They establish as a low-copy-number plasmid. Their stability was estimated by measuring loss of the plasmid after 25 generations of unselected growth (15).

	RESULTS

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The P1par family of plasmid partition systems. There are currently five clearly distinct sequences closely related to the P1par operon (6, 22, 31, 23, 27). They are present in a variety of different plasmid types from five different gram-negative bacterial genera. The six resulting P1par family members form a compact clade, with both Par proteins showing high degrees of similarity to their P1 counterparts (12). Each of the six P1par family members has adjacent open reading frames for the ParA and ParB proteins of similar sizes and in the same order as those of P1. Previously described members have functional parS sites placed closely downstream of the parB gene (24, 31). A search of the regions downstream of parB in the remaining members showed that these also have candidate parS sites. An alignment of the six sequences is shown in Fig. 1. This alignment is in close agreement with that recently proposed by Funnell and Slavcev (12). In the case of Rts1parS, the proposed site does not correspond to the potential IHF binding site and partition site mentioned in the annotated sequence AP004237.1 (23).

View larger version (74K): [in this window] [in a new window]   FIG. 1. Alignments of key sequences from the par regions of P1par family members. Top: The regions corresponding to the P1parS site are aligned. Shading identifies bases that are identical to P1parS. Center: The BoxB sequences within parS are compared. Bottom: Portions of the ParB protein sequences near the carboxy termini are aligned. Numbers indicate the amino acid positions in the ParB open reading frame. Shading identifies amino acids that are identical or similar to those of P1 ParB. Similarities are shown as white letters. The bold, underlined sequences contain the DRS regions shown to be involved in the ParB-BoxB contacts in P1 and P7par.

In the P1 and P7 cases, the region of the ParB protein that contacts BoxB, the DRS, has been mapped. In both cases, it lies near the C terminus of the protein (25) (Fig. 1). If BoxB contacts the equivalent ParB regions in all family members, there should be a correlation between the similarities of the BoxB sequences and the similarities in the contacting ParB DRSs. Alignment of the regions surrounding the putative DRSs of the six ParB proteins (Fig. 1) shows that the three members with identical or very similar BoxB sequences (P1, pSLT, pWR100) also have similar ParB contact regions. The equivalent regions in the three members with unique BoxB sequences are dissimilar from those of the P1 group and from each other. This correlation fits with the currently known species specificities of the systems: P1 and pWR100 have identical specificities (27), whereas those of P7 and pMT1 are different from P1 and each other (31). Based on the analysis in Fig. 1, we predict that, of the two members remaining uncharacterized, pSLTpar will prove to have identical specificity to P1, whereas Rts1par will show a unique specificity.

A specificity test for partition with Par proteins produced from the E. coli chromosome. We have recently shown that a P1 miniplasmid carrying P1parS is properly maintained when the P1 ParA and ParB proteins are supplied from an insert in the E. coli host chromosome (20). The P1par operon was integrated at att and was expressed from an attenuated plac promoter (20). This type of construct is preferable for genetic studies of partition because the par operons and parS sites can be tested in different combinations without the necessity of maintaining more than one plasmid in the cell. Also, the test system is free from complications imposed by par operon autoregulation. We constructed similar strains carrying the par operons from pMT1 and P7 integrated into the chromosome (see Materials and Methods). The maintenance of the appropriate parS-containing plasmids in these strains is shown in Table 1. Each strain maintained the cognate parS plasmid when the appropriate ParA and ParB proteins were supplied from the chromosome. This confirms our previous findings, made with a plasmid-borne par operon, that the Y. pestis pMT1 par system works well in E. coli and that Par proteins work in trans to the partitioning plasmid (31). By introducing the parS plasmids into strains with different par operons, the species specificities of the parS sites were also readily demonstrated. Thus, as found previously using plasmid-borne par operons, the Par proteins of P1, P7, and pMT1 are not interchangeable. They worked only with the cognate P1parS, P7parS, and pMT1parS sites, respectively (Table 1).

View this table: [in this window] [in a new window]   TABLE 1. Retention of -miniP1parS-containing plasmids with Par proteins supplied from the E. coli chromosome

The hybrid parS sites were incorporated into a miniP1 plasmid and supplied with the appropriate Par proteins expressed from the host chromosome. Their stabilities were determined in a partition test by measuring the loss of the composite plasmid after 25 generations of unselected growth. The wild-type pMT1parS site responded only to the pMT1 Par proteins (Table 2). Substitutions of both BoxB sequences of the pMT1parS site gave a complete switch in specificity. When the P1 BoxB sequences were substituted for their equivalents in the pMT1parS site, the plasmid was stabilized by the P1 Par proteins but not by the pMT1 proteins. When the P7 BoxB sequences were introduced, the plasmid was stabilized by the P7 Par proteins but not by the pMT1 proteins (Table 2).

View this table: [in this window] [in a new window]   TABLE 2. Retention of hybrid -miniP1parS-containing plasmids with Par proteins supplied from the E. coli chromosome

A single modification in the pMT1parS site can change species specificity. To examine further the pMT1parS species specificity, we obtained single mutations in the left or right BoxB sequence. The resulting hybrid pMT1parS plasmids with P1 nucleotide substitutions were tested with the pMT1 and P1 Par proteins (Table 3). Substitution of just BoxB2 of pMT1 with the equivalent P1 sequence was sufficient to change the specificity of the site completely from pMT1 to the P1 type. This substitution involves the change of only a single base. Substitution of the equivalent base in BoxB1 also caused a specificity switch: the hybrid site lost all activity with the pMT1 proteins but responded to the P1 proteins, albeit with a much-reduced activity (Table 3). Thus, a single base change in either of the two BoxB sequences is sufficient to change the species specificity. There are 27 base pairs that differ between the 82-bp P1parS and pMT1parS sites (Fig. 1). All but the one critical base pair in BoxB appear to be uninformative as far as species specificity is concerned.

	DISCUSSION

Top Abstract Introduction Materials and Methods Results Discussion References

 
We show that the information for species specificity of the pMT1par system resides in a critical nucleotide sequence within the BoxB hexamer-encoding motif of parS. Unique variations in the BoxB-encoding nucleotide sequence define the species differences between at least three different P1par family members: pMT1par, P1par, and P7par. BoxB and the DRS that it contacts appear to constitute a special mechanism for defining species specificity in the P1par family of elements. Deletion of both P1 BoxB repeats does not prevent ParB binding (24). However, the species specificity for ParB binding is now eliminated. The site no longer binds P1 ParB exclusively but can bind P7 ParB equally well (24). Thus, the parS BoxB-ParB contact appears to govern ParB binding in an essentially negative sense: it prevents the wrong type of ParB protein from binding to a site that could otherwise accept it (25). The shape of the parS DNA may facilitate this discrimination. IHF binding at the center of the site bends it into a loop (10, 14). P1parS fails to discriminate between P1 and P7 ParB binding in the absence of IHF (25). It seems likely that an inappropriate match between ParB and the BoxB motifs causes an interference that prevents the proper positioning of ParB in the structured loop of the DNA. The BoxB discriminator contact can adopt at least three exclusive configurations that define three different species specificities.

Relatively little information is needed to change specificity from one type to another. As shown here, a single base difference is sufficient to convert pMT1parS to P1 specificity. This result is somewhat surprising, because the altered site still has one BoxB of the pMT1 type and yet retains no function in the presence of the pMT1 proteins. Perhaps the pMT1 system has more-stringent requirements than those for P1, such that both boxes must be of the pMT1 type. In any case, the parS information for species specificity is limited to just a few BoxB bases. Based on our knowledge of the P1 and P7 DRSs (26), the necessary information in the protein is also likely to be limited. This presumably allows new species specificities to arise by mutation relatively easily. Thus, the plasticity of the BoxB-DRS contact may facilitate speciation as these plasmids evolve.

What advantage, if any, is gained by par system speciation? If a plasmid enters a cell containing another plasmid with the same type of partition system, the resident is often displaced due to partition-mediated incompatibility (2). The three members of the P1par family studied here have different incompatibility specificities. They do not interfere with each other in this way. The development of a new incompatibility type would be an advantage to an evolving plasmid: it would no longer have to compete for partition with its progenitors. Here, we show evidence that incompatibility specificity and species specificity are codetermined. Thus, the species specificity differences between P1par family members probably evolved as a means of overcoming competition due to partition-mediated incompatibility.

Partition-mediated incompatibility can be changed by subtle alterations in the parS BoxB sequence, sometimes involving only a single base change. As evidenced by the P1 and P7 cases, this sequence contacts ParB and determines which species of ParB protein will be recognized. Thus, incompatibility appears to be determined not by the bulk of the parS sequence but by the type of ParB protein that is recruited to it. A number of mechanisms have been proposed for partition-mediated incompatibility. These include the down-regulation of Par protein synthesis by trans effects of additional parS sites on par operon autoregulation (4), the formation of mixed pairs of plasmids via parS prior to segregation (2), and the titration of a limited pool of Par proteins by the competing sites (19). Any effects on operon autoregulation can be ruled out, at least in our experiments, as the Par proteins are constitutively expressed. However, our results are consistent with either or both of the latter explanations. Plasmid pairing likely involves specific contacts between bound ParB proteins (8), and titration would depend on recruitment of the same ParB protein to the competing plasmids.

	FOOTNOTES

 
* Corresponding author. Mailing address: Gene Regulation & Chromosome Biology Laboratory, National Cancer Institute, CCR, NCI-Frederick, Frederick, MD 21702-1201. Phone: (301) 846-1266. Fax: (301) 846-6988. E-mail: austin{at}ncifcrf.gov.

	REFERENCES

Top Abstract Introduction Materials and Methods Results Discussion References

 

1. Abeles, A. L., S. A. Friedman, and S. J. Austin. 1985. Partition of unit-copy miniplasmids to daughter cells. III. The DNA sequence and functional organization of the P1 partition region. J. Mol. Biol. 185:261-272.[CrossRef][Medline]
2. Austin, S. J., and K. Nordstrom. 1990. Partition-mediated incompatibility of bacterial plasmids. Cell 60:351-354.[CrossRef][Medline]
3. Bork, P., C. Sander, and A. Valencia. 1992. An ATPase domain common to prokaryotic cell cycle proteins, sugar kinases, actin, and hsp70 heat shock proteins. Proc. Natl. Acad. Sci. USA 89:7290-7294.[Abstract/Free Full Text]
4. Bouet, J. Y., J. Rech, S. Egloff, D. P. Biek, and D. Lane. 2005. Probing plasmid partition with centromere-based incompatibility. Mol. Microbiol. 55:511-525.[CrossRef][Medline]
5. Boyd, D., D. S. Weiss, J. C. Chen, and J. Beckwith. 2000. Towards single-copy gene expression systems making gene cloning physiologically relevant: lambda InCh, a simple Escherichia coli plasmid-chromosome shuttle system. J. Bacteriol. 182:842-847.[Abstract/Free Full Text]
6. Cerin, H., and J. Hackett. 1993. The parVP region of the Salmonella typhimurium virulence plasmid pSLT contains four loci required for incompatibility and partition. Plasmid 30:30-38.[CrossRef][Medline]
7. Davis, M. A., and S. J. Austin. 1988. Recognition of the P1 plasmid centromere analog involves binding of the ParB protein and is modified by a specific host factor. EMBO J. 7:1881-1888.[Medline]
8. Edgar, R., D. K. Chattoraj, and M. Yarmolinsky. 2001. Pairing of P1 plasmid partition sites by ParB. Mol. Microbiol. 42:1363-1370.[CrossRef][Medline]
9. Ferber, D. M., and R. R. Brubaker. 1981. Plasmids in Yersinia pestis. Infect. Immun. 31:839-841.[Abstract/Free Full Text]
10. Funnell, B. E. 1991. The P1 plasmid partition complex at parS. The influence of Escherichia coli integration host factor and of substrate topology. J. Biol. Chem. 266:14328-14337.[Abstract/Free Full Text]
11. Funnell, B. E. 1988. Participation of Escherichia coli integration host factor in the P1 plasmid partition system. Proc. Natl. Acad. Sci. USA 85:6657-6661.[Abstract/Free Full Text]
12. Funnell, B. E., and R. A. Slavcev. 2004. Partition systems of bacterial plasmids, p. 81-104. In B. E. Funnell and G. J. Phillips (ed.), Plasmid biology. ASM Press, Washington, D.C.
13. Gerdes, K., J. Moller-Jensen, and R. Bugge Jensen. 2000. Plasmid and chromosome partitioning: surprises from phylogeny. Mol. Microbiol. 37:455-466.[CrossRef][Medline]
14. Hayes, F., and S. Austin. 1994. Topological scanning of the P1 plasmid partition site. J. Mol. Biol. 243:190-198.[CrossRef][Medline]
15. Hayes, F., and S. J. Austin. 1993. Specificity determinants of the P1 and P7 plasmid centromere analogs. Proc. Natl. Acad. Sci. USA 90:9228-9232.[Abstract/Free Full Text]
16. Hayes, F., M. A. Davis, and S. J. Austin. 1993. Fine-structure analysis of the P7 plasmid partition site. J. Bacteriol. 175:3443-3451.[Abstract/Free Full Text]
17. Helsberg, M., and R. Eichenlaub. 1985. Twelve 43-base-pair repeats map in a cis-acting region essential for partition of plasmid mini-F. J. Bacteriol. 165:1043-1045.
18. Koonin, E. V. 1993. A common set of conserved motifs in a vast variety of putative nucleic acid-dependent ATPases including MCM proteins involved in the initiation of eukaryotic DNA replication. Nucleic Acids Res. 21:2541-2547.[Abstract/Free Full Text]
19. Lane, D., R. Rothenbuehler, A.-M. Merrillat, and C. Aiken. 1987. Analysis of the F plasmid centromere. Mol. Gen. Genet. 207:406-412.[CrossRef][Medline]
20. Li, Y., A. Dabrazhynetskaya, B. Youngren, and S. Austin. 2004. The role of Par proteins in the active segregation of the P1 plasmid. Mol. Microbiol. 53:93-102.[CrossRef][Medline]
21. Lindler, L. E., G. V. Plano, V. Burland, G. F. Mayhew, and F. R. Blattner. 1998. Complete DNA sequence and detailed analysis of the Yersinia pestis KIM5 plasmid encoding murine toxin and capsular antigen. Infect. Immun. 66:5731-5742.[Abstract/Free Full Text]
22. Ludtke, D. N., B. G. Eichorn, and S. J. Austin. 1989. Plasmid-partition functions of the P7 prophage. J. Mol. Biol. 209:393-406.[CrossRef][Medline]
23. Murata, T., M. Ohnishi, T. Ara, J. Kaneko, C. G. Han, Y. F. Li, K. Takashima, H. Nojima, K. Nakayama, A. Kaji, Y. Kamio, T. Miki, H. Mori, E. Ohtsubo, Y. Terawaki, and T. Hayashi. 2002. Complete nucleotide sequence of plasmid Rts1: implications for evolution of large plasmid genomes. J. Bacteriol. 184:3194-3202.[Abstract/Free Full Text]
24. Radnedge, L., M. A. Davis, and S. J. Austin. 1996. P1 and P7 plasmid partition: ParB protein bound to its partition site makes a separate discriminator contact with the DNA that determines species specificity. EMBO J. 15:1155-1162.[Medline]
25. Radnedge, L., B. Youngren, M. Davis, and S. Austin. 1998. Probing the structure of complex macromolecular interactions by homolog specificity scanning: the P1 and P7 plasmid partition systems. EMBO J. 17:6076-6085.[CrossRef][Medline]
26. Sambrook, J., E. F. Fritsch, and T. Maniatis. 1989. Molecular cloning: a laboratory manual, 2nd ed. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.
27. Sergueev, K., A. Dabrazhynetskaya, and S. Austin. 2005. Plasmid partition system of the P1par family from the pWR100 virulence plasmid of Shigella flexneri. J. Bacteriol. 187:3369-3373.[Abstract/Free Full Text]
28. Surtees, J. A., and B. E. Funnell. 2001. The DNA binding domains of P1 ParB and the architecture of the P1 plasmid partition complex. J. Biol. Chem. 276:12385-12394.[Abstract/Free Full Text]
29. Surtees, J. A., and B. E. Funnell. 2003. Plasmid and chromosome traffic control: how ParA and ParB drive partition. Curr. Top. Dev. Biol. 56:145-180.[Medline]
30. Weiss, D. S., J. C. Chen, J. M. Ghigo, D. Boyd, and J. Beckwith. 1999. Localization of FtsI (PBP3) to the septal ring requires its membrane anchor, the Z ring, FtsA, FtsQ, and FtsL. J. Bacteriol. 181:508-520.[Abstract/Free Full Text]
31. Youngren, B., L. Radnedge, P. Hu, E. Garcia, and S. Austin. 2000. A plasmid partition system of the P1-P7par family from the pMT1 virulence plasmid of Yersinia pestis. J. Bacteriol. 182:3924-3928.[Abstract/Free Full Text]
32. Yu, D., H. M. Ellis, E. C. Lee, N. A. Jenkins, N. G. Copeland, and D. L. Court. 2000. An efficient recombination system for chromosome engineering in Escherichia coli. Proc. Natl. Acad. Sci. USA 97:5978-5983.[Abstract/Free Full Text]

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