38] Cardiolipin synthase from Escherichia coli

Abstract

Publisher Summary In Escherichia coli (E.coli), cardiolipin is mainly synthesized by cardiolipin synthase, encoded by the cls gene, via condensation of two molecules of phosphatidylglycerol, also yielding one molecule of glycerol. This contrasts with the eukaryotic enzymes that condense CDPdiacylglycerol and phosphatidylglycerol to form cardiolipin and cytidine monophosphate (CMP). The biological implication of the metabolically uneconomical pathway in E. coli is unknown. The E. coli cardiolipin synthase is present exclusively in the envelope (crude membrane) fraction of the cell. The E. coli cls null mutants that are completely devoid of cardiolipin synthase activity grow well and form small amounts of cardiolipin, suggesting that E. coli possesses an alternative minor pathway to form cardiolipin. The most likely candidate responsible for this second pathway is phosphatidylserine synthase. It has been suggested that cardiolipin synthase may catalyze practically reversible reactions, and its relaxed substrate specificity may allow the formation of lyso- and dilysocardiolipins from 2-acyllysophosphatidylglycerol and a series of analogs of phosphatidylglycerol and cardiolipin if high concentrations of the appropriate straight-chain sugar alcohols are present in the culture medium.