IMMUNOCYTOCHEMICAL LOCALIZATION OF ACYL-LIPID DESATURASES IN CYANOBACTERIAL CELLS - EVIDENCE THAT BOTH THYLAKOID MEMBRANES AND CYTOPLASMIC MEMBRANES ARE SITES OF LIPID DESATURATION

There are four acyl-lipid desaturases in the cyanobacterium Synechocys tis sp. PCC 6803. Each of these desaturases introduces a double bond a t a specific position, such as the Delta 6, Delta 9, Delta 12, or omeg a 3 position, in C-18 fatty acids. The localization of the desaturases in cyanobacterial cells was examined immunocytochemically with antibo dies raised against synthetic oligopeptides that corresponded to the c arboxyl-terminal regions of the desaturases. All four desaturases appe ared to be located in the regions of both the cytoplasmic and the thyl akoid membranes. These findings suggest that fatty acid desaturation o f membrane lipids takes place in the thylakoid membranes as well as in the cytoplasmic membranes.