Differential acylation in vitro with tetradecanoyl coenzyme A and tetradecanoic acid (+ATP) of three polypeptides shown to have induced synthesis in Photobacterium phosphoreum.

Abstract

Acylation of extracts of Photobacterium phosphoreum at different stages of growth with [3H]tetradecanoic acid (+ATP) has shown that two polypeptides found in the fatty acid reductase complex, the fatty acid activating enzyme (50K) and the 34K polypeptide, were specifically labeled during induction of the luminescent system. An alternate method for in vitro acylation of polypeptides in the luminescent system was developed using tetradecanoyl-CoA. Both the 34K polypeptide and, to a lesser extent, the acyl-CoA reductase component (58K) in the complex, were acylated with [3H]tetradecanoyl-CoA. In contrast, the fatty acid activating enzyme (50K) was not labeled. Labeling of both the 34K and 58K polypeptides with [3H]tetradecanoyl-CoA as well as the acyl-CoA reductase activity in extracts paralleled the induction of luciferase during growth. Differential labeling of P. phosphoreum cells with [35S]methionine before luminescence induction and with [3H]methionine after the onset of luminescence followed by purification of luciferase and the polypeptides in the fatty acid reductase complex demonstrated that the alpha and beta subunits of luciferase and the 34K, 50K, and 58K polypeptides of the complex had 3H/35S ratios at least 7-fold higher than the constitutive proteins. These results give evidence that the synthesis of the component polypeptides of the fatty acid reductase are induced during the development of bioluminescence and may be under the same control as luciferase. The experiments also showed that P. phosphoreum may have the highest content of luciferase of any luminescent bacterium, constituting approximately 20% of the total soluble protein in extracts.