THE LIPA GENE OF SERRATIA-MARCESCENS WHICH ENCODES AN EXTRACELLULAR LIPASE HAVING NO N-TERMINAL SIGNAL PEPTIDE

The lipA gene encoding an extracellular lipase was cloned from the wil d-type strain of Serratia marcescens Sr41. Nucleotide sequencing showe d a major open reading frame encoding a 64.9-kDa protein of 613 amino acid residues; the deduced amino acid sequence contains a lipase conse nsus sequence, GXSXG. The lipase had 66 and 56% homologies with the li pases of Pseudomonas fluorescens B52 and P.fluorescens SIK W1, respect ively, but did not show any overall homology with lipases from other o rigins. The Escherichia coli cells carrying the S. marcescens lipA gen e did not secrete the lipase into the medium. The S. marcescens lipase had no conventional N-terminal signal sequence but was also not subje cted to any processing at both the N-terminal and C-terminal regions. A specific short region similar to the regions of secretory proteins h aving no N-terminal signal peptide was observed in the amino acid sequ ence. Expression of the lipA gene in S. marcescens was affected by the carbon source and the addition of Tween 80.