NUCLEOTIDE-SEQUENCE ANALYSIS OF POG32, A CRYPTIC PLASMID FROM LEUCONOSTOC-OENOS

Analysis of the nucleotide sequence of Leuconostoc oenos plasmid pOg32 (2544 bp) revealed three open reading frames (ORFs) in one of the DNA strands preceded by putative promoters and ribosome binding sites. OR F1 corresponded to a polypeptide similar to the replication proteins ( Rep) of pT181 plasmid family. A nucleotide sequence like the double st rand origin (DSO) of the same plasmid family was found inside the pres umptive rep gene. ORF2 is capable of encoding a protein resembling the recombination enzyme (Pre) of two lactobacilli plasmids. Immediately upstream of the presumed pie gene, a sequence similar to the consensus RS(A) regions of those plasmids was encountered. Between ORF3 and ORF 1, a sequence comparable to the RS(B) consensus region of the single s trand origin ssoA was detected. The putative RS(B) region was located at the 3'-end of an imperfect palindrome which may be a single strande d origin. The described features, common to other small plasmids of Gr am-positive bacteria, suggest that pOg32 replicates by the rolling cir cle mechanism. The amino acid sequence encoded by ORF3 was not similar to any known protein. (C) 1996 Academic Press, Inc.