INVESTIGADORES
AGUILAR Pablo S.
artículos
Título:
A Bacillus subtilis gene induced by cold shock encodes a membrane phospholipid desaturase.
Autor/es:
AGUILAR PABLO S., CRONAN JOHN E. JR., AND DE MENDOZA DIEGO.
Revista:
JOURNAL OF BACTERIOLOGY
Editorial:
American Society for Microbiology
Referencias:
Lugar: Washington DC; Año: 1998 vol. 180 p. 2194 - 2200
ISSN:
0021-9193
Resumen:
Bacillus subtilis grown at 37°C synthesizes saturated fatty acids with only traces of unsaturated fatty acids
(UFAs). However, when cultures growing at 37°C are transferred to 20°C, UFA synthesis is induced. We report
the identification and characterization of the gene encoding the fatty acid desaturase of B. subtilis. This gene,
called des, was isolated by complementation of Escherichia coli strains with mutations in either of two different
genes of UFA synthesis. The des gene encodes a polypeptide of 352 amino acid residues containing the three
conserved histidine cluster motifs and two putative membrane-spanning domains characteristic of the membrane-
bound desaturases of plants and cyanobacteria. Expression of the des gene in E. coli resulted in
desaturation of palmitic acid moieties of the membrane phospholipids to give the novel mono-UFA cis-5-
hexadecenoic acid, indicating that the B. subtilis des gene product is a Δ5 acyl-lipid desaturase. The des gene
was disrupted, and the resulting null mutant strains were unable to synthesize UFAs upon a shift to low growth
temperatures. The des null mutant strain grew as well as its congenic parent at 20 or 37°C but showed severely
reduced survival during stationary phase. Analysis of operon fusions in which the des promoter directed the
synthesis of a lacZ reporter gene showed that des expression is repressed at 37°C, but a shift of cultures from
37 to 20°C resulted in a 10- to 15-fold increase in transcription. This is the first report of a membrane phospholipid
desaturase in a nonphotosynthetic organism and the first direct evidence for cold induction of a desaturase.