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J. Bacteriol., Dec 1995, 7026-7032, Vol 177, No. 24
K Kahn and MR Schaefer
A transposon, designated Tn5469, was isolated from mutant strain FdR1 of
the filamentous cyanobacterium Fremyella diplosiphon following its
insertion into the rcaC gene. Tn5469 is a 4,904-bp noncomposite transposon
with 25-bp near-perfect terminal inverted repeats and has three tandemly
arranged, slightly overlapping potential open reading frames (ORFs)
encoding proteins of 104.6 kDa (909 residues), 42.5 kDa (375 residues), and
31.9 kDa (272 residues). Insertion of Tn5469 into the rcaC gene in strain
FdR1 generated a duplicate 5-bp target sequence. On the basis of amino acid
sequence identifies, the largest ORF, designated tnpA, is predicted to
encode a composite transposase protein. A 230-residue domain near the amino
terminus of the TnpA protein has 15.4% amino acid sequence identity with a
corresponding domain for the putative transposase encoded by Lactococcus
lactis insertion sequence S1 (ISS1). In addition, the sequence for the
carboxyl-terminal 600 residues of the TnpA protein is 20.0% identical to
that for the TniA transposase encoded by Tn5090 on Klebsiella aerogenes
plasmid R751. The TnpA and TniA proteins contain the D,D(35)E motif
characteristic of a recently defined superfamily consisting of bacterial
transposases and integrase proteins of eukaryotic retroelements and
retrotransposons. The two remaining ORFs on Tn5469 encode proteins of
unknown function. Southern blot analysis showed that wild-type F.
diplosiphon harbors five genomic copies of Tn5469. In comparison, mutant
strain FdR1 harbors an extra genomic copy of Tn5469 which was localized to
the inactivated rcaC gene. Among five morphologically distinct
cyanobacterial strains examined, none was found to contain genomic
sequences homologous to Tn5469.
Copyright © 1995, American Society for Microbiology
Characterization of transposon Tn5469 from the cyanobacterium Fremyella diplosiphon
Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City 64110, USA.
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