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J. Bacteriol., 12 1997, 7843-7855, Vol 179, No. 24
H Tomita, S Fujimoto, K Tanimoto and Y Ike
The pheromone-responsive conjugative plasmid pPD1 (59 kb) of Enterococcus
faecalis encodes the bacteriocin 21 (bac21) determinant. Cloning,
transposon insertion mutagenesis and sequence analysis of the bac21
determinant showed that an 8.5-kb fragment lying between kb 27.1 and 35.6
of the pPD1 map is required for complete expression of the bacteriocin. The
8.5-kb fragment contained nine open reading frames (ORFs), bacA to bac1,
which were oriented in the same (upstream-to- downstream) direction.
Transposon insertions into the bacA to bacE ORFs, which are located in the
proximal half of bac21, resulted in defective bacteriocin expression.
Insertions into the bacF to bac1 ORFs, which are located in the distal half
of bac21, resulted in reduced bacteriocin expression. Deletion mutant
analysis of the cloned 8.5-kb fragment revealed that the deletion of
segments between kb 31.6 and 35.6 of the pPD1 map, which contained the
distal region of the determinant encoding bacF to bac1, resulted in reduced
bacteriocin expression. The smallest fragment (4.5 kb) retaining some
degree of bacteriocin expression contained the bacA to bacE sequences
located in the proximal half of the determinant. The cloned fragment
encoding the 4.5-kb proximal region and a Tn916 insertion mutant into pPD1
bacB trans-complemented intracellularly to give complete expression of the
bacteriocin. bacA encoded a 105-residue sequence with a molecular mass of
11.1 kDa. The deduced BacA protein showed 100% homology to the broad-
spectrum antibiotic peptide AS-48, which is encoded on the E. faecalis
conjugative plasmid pMB2 (58 kb). bacH encoded a 195-residue sequence with
a molecular mass of 21.9 kDa. The deduced amino acid sequence showed
significant homology to the C-terminal region of HlyB (31.1% identical
residues), a protein located in the Escherichia coli alpha- hemolysin
operon that is a representative bacterial ATP-binding cassette export
protein.
Copyright © 1997, American Society for Microbiology
Cloning and genetic and sequence analyses of the bacteriocin 21 determinant encoded on the Enterococcus faecalis pheromone-responsive conjugative plasmid pPD1
Department of Microbiology, Gunma University School of Medicine, Maebashi, Japan.
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