Abstract
Digalactosyldiacylglycerol (DGDG) is one of the lipid molecules present in thylakoid membranes. DGDG exists not only as a lipid bilayer-forming molecule but also as a component of various complexes in thylakoid membranes. It has been reported that fourteen lipid molecules were bound to photosystem II complex (PSII) of Thermosynechococcus elongatus, and four of them were DGDG. Although the findings suggest that DGDG plays important roles in PSII, its physiological role has not been clarified.
Search with our Gclust server (http://gclust.c.u-tokyo.ac.jp/) predicted that a novel DGDG synthase, which is different from that of higher plants, is conserved among several cyanobacteria and Cyanidioschyzon merolae. Disruption of slr1508 gene in Synechocystis sp. PCC 6803 resulted in a loss of ability to synthesize DGDG. With this mutant, we found that DGDG is not an essential component of PSII, but is required for stabilization of PSII.
