BIOSYNTHESIS AND FUNCTION OF THE SULFOLIPID SULFOQUINOVOSYL DIACYLGLYCEROL

The sulfolipid sulfoquinovosyl diacylglycerol is an abundant sulfur-co ntaining nonphosphorous glycerolipid that is specifically associated w ith photosynthetic membranes of higher plants, mosses, ferns, algae, a nd most photosynthetic bacteria. The characteristic structural feature of sulfoquinovosyl diacylglycerol is the unique head group constituen t sulfoquinovose, a derivative of glucose in which the B-hydroxyl is r eplaced by a sulfonate group. While there is growing evidence for the final assembly of the sulfolipid by the transfer of the sulfoquinovosy l moiety from UDP-sulfoquinovose to the sn-3 position of diacylglycero l, very little is known about the biosynthesis of the precursor UDP-su lfoquinovose. Recently, a number of mutants deficient in sulfolipid bi osynthesis and the corresponding sqd genes have become available from different organisms. These provide novel tools to analyze sulfolipid b iosynthesis by a combination of molecular and biochemical approaches. Furthermore, the analysis of sulfolipid-deficient mutants has provided novel insights into the function of sulfoquinovosyl diacylglycerol in photosynthetic membranes.