Cloning and sequence analysis of the lipase and lipase chaperone-encoding genes from Acinetobacter calcoaceticus RAG-1, and redefinition of a Proteobacterial lipase family and an analogous lipase chaperone family

The genes encoding the lipase (LipA) and lipase chaperone (LipB) from Acine tobacter calcoaceticus RAG-1 were cloned and sequenced. The genes were isol ated from a genomic DNA library by complementation of a lipase-deficient tr ansposon mutant of the same strain. Transposon insertion in this mutant and three others was mapped to a single site in the chaperone gene. The deduce d amino acid (aa) sequences for the lipase and its chaperone were found to encode mature proteins of 313 aa (32.5 kDa) and 347 aa (38.6 kDa), respecti vely. The lipase contained a putative leader sequence, as well as the conse rved Ser, His, and Asp residues which are known to function as the catalyti c triad in other Lipases, A possible trans-membrane hydrophobic helix was i dentified in the N-terminal region of the chaperone. Phylogenetic compariso ns showed that LipA, together with the lipases of A. calcoaceticus BD413, V ibrio cholerae El Tor, and Proteus vulgaris K80, were members of a previous ly described family of Pseudomonas and Burkholderia lipases. This new famil y, which we redefine as the Group I Proteobacterial lipases, was subdivided into four subfamilies on the basis of overall sequence homology and conser vation of residues which are unique to the subfamilies. LipB, moreover, was found to be a member of an analogous family of lipase chaperones. We propo se that the lipases produced by P. fluorescens and Serratia marcescens, whi ch comprise a second sequence family, be referred to as the Group II Proteo bacterial lipases. Evidence is provided to support the hypothesis that both the Group I and Group II families have evolved from a combination of commo n descent and lateral gene transfer. (C) 1999 Elsevier Science B.V. All rig hts reserved.