PERIPLASMIC LOCATION OF THE PESTICIN IMMUNITY PROTEIN SUGGESTS INACTIVATION OF PESTICIN IN THE PERIPLASM

The pesticin activity and immunity genes on plasmid pPCP1 of Yersinia pestis were sequenced. They encoded proteins of 40 kDa (pesticin) and 16 kDa (immunity protein); the latter was found in the periplasm. The location of the immunity protein suggests that imported pesticin is in activated in the periplasm before it hydrolyzes murein. Pesticin conta ins a TonB box close to the N-terminal end that is identical to the To nB box of colicin B. The DNA sequences flanking the pesticin determina nt were highly homologous to those flanking the colicin 10 determinant . It is proposed that through these highly homologous DNA sequences, g enes encoding bacteriocins may be exchanged between plasmids by recomb ination. In the case of pesticin, recombination may have destroyed the lysis gene,of which only a rudimentary fragment exists on pPCP1.