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J. Bacteriol., Jun 1996, 3194-3200, Vol 178, No. 11
KG Anthony, P Kathir, D Moore, K Ippen-Ihler and LS Frost
The sequence of a region of the F plasmid containing the traLEKBP genes
involved in plasmid transfer was compared to the equivalent regions of two
IncFII plasmids, R100-1 and ColB2. The traLEK gene products of all three
plasmids were virtually identical, with the most changes occurring in TraE.
The TraB genes were also nearly identical except for an 11-codon extension
at the 3' end of the R100-1 traB gene. The TraP protein of R100-l differed
from those of F and ColB2 at its N terminus, while the ColB2 TraP protein
contained a change of sequence in a predicted loop which was shown to be
exposed in the periplasmic space by TnphoA mutagenesis. The effect of the
altered TraP sequences was determined by complementing a traP mutant with
clones expressing the traKBP genes of F, R100-1, and ColB2. The traP
mutation in pOX38 (pOX38- traP474), a derivative of F, was found to have
little effect on pilus production, pilus retraction, and filamentous phage
growth and only a moderate effect on transfer. The transfer ability of
pOX38-traP474 was shown to be affected by mutations in the rfa
(lipopolysaccharide) locus and in ompA in the recipient cell in a manner
similar to that for the wild-type pOX38-Km plasmid itself and could be
complemented with the traP analogs from R100-1 and ColB2 to give an F-like
phenotype. Thus, the TraP protein appears to play a minor role in
conjugation and may interact with TraB, which varies in sequence along with
TraP, in order to stabilize the proposed transmembrane complex formed by
the tra operon products.
Copyright © 1996, American Society for Microbiology
Analysis of the traLEKBP sequence and the TraP protein from three F- like plasmids: F, R100-1 and ColB2
Department of Biological Sciences, University of Alberta, Edmonton, Canada.
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