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
Er. Sullivan et al., 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, GENE, 230(2), 1999, pp. 277-285
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.