Cloning and characterizations of the Serratia marcescens metK and pfs genes involved in AI-2-dependent quorum-sensing system

Serratia marcescens utilizes two types of quorum-sensing signal molecules: N-acyl homoserine lactones and furanosyl borate diester (AI-2). S-adenosylmethionine synthetase (METK), S-adenosylhomocysteine nucleosidase (PFS), and S-ribosylhomocysteinase (LUXS) are three key enzymes in the biosynthetic pathway leading to AI-2 production. The sequence of luxS gene was published at NCBI (Accession number: EF164926). So in this study, Serratia marcescens metK and pfs genes were successfully cloned with inverse PCR. The results show that the ORF lengths of metK and pfs are 1155 and 702 bp, and encode proteins of 384 and 233 residues. Their molecular weights and isoelectric points are 41.85 kD and 5.50; 27.67 kD and 5.56, which are acidic proteins judging from the calculated pI values. Expression products of two genes with pET28a((+)) system exhibited molecular weights in sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis comparable with a theoretical estimation. The sequences of these two genes were conferred China patent application numbers CN 200710048016.X and CN 200710048015.5, respectively.