Abstract
In both chloroplasts of higher plants and cyanobacteria half of the membrane lipid is monogalactosyldiacylglycerol (MGDG). The MGDG synthesis pathway is very different between them. In chloroplasts the MGDG synthesis is one-step reaction catalyzed by MGDG synthase, while in cyanobacteria it is two-step reaction catalyzed by monoglucosyldiacylglycerol (MGlcDG) synthase followed by the epimerization of MGlcDG to generate MGDG. Gloeobacter violaceus PCC 7421 that is known to be branched off at the earliest stage in the cyanobacterial clade have genes very similar to cyanobacterial MGlcDG synthase and plant MGDG synthase (Awai et al., unpublished). We expressed the two genes in Escherichia coli and analyzed the glycosyltransferase activities. The results showed that the both proteins had the activity of MGlcDG synthase while they had no activity of MGDG synthase. We will show more in detail the biochemical and enzymatic properties of the two proteins after purification.
