Functional identification of the fatty acid reductase components encoded in the luminescence operon of Vibrio fischeri

Abstract

A clone of DNA, obtained from the luminescent bacterium Vibrio fischeri ATCC 7744 and inserted into pBR322, was found to express luminescence in Escherichia coli. Polypeptides involved in biosynthesis of the fatty aldehyde substrate for the light reaction were identified by fatty acid acylation of proteins synthesized in E. coli from the recombinant plasmid. The cloned region was similar to that reported for the V. fischeri MJ1 luminescence system (Engebrecht et al., Cell 32:773-781), except for some differences in endonuclease restriction sites and the requirement of a lower temperature for the expression of light in our cloned system. Fatty acid reductase activity could be detected in extracts of E. coli harboring the recombinant plasmid but not in extracts of the parental V. fischeri strain. Using in vivo labeling with [3H]tetradecanoic acid, we showed that the acylated polypeptides synthesized in the cloned system corresponded to the labeled polypeptides in V. fischeri (34, 42, and 54 kilodaltons) and that they could only be detected after induction of luminescence. These results provide direct evidence that the genes coding for the fatty acid reductase polypeptides are an integral part of the luminescence operon in the V. fischeri luminescence system.