POSTTRANSLATIONAL MODIFICATION OF PROTEINS WITH FATTY-ACIDS IN PLATELETS

Direct modification of proteins by fatty acid can occur as cotranslati onal N-myristoylation of an N-terminal glycine residue or as posttrans lational thioesterification of cysteine residue(s), Platelets provide an excellent model system for studying the posttranslational type of m odification in the absence of active protein synthesis and in the abse nce of protein synthesis-related protein modifications with lipids. Us ing this model system it was shown that thioesterification of proteins with fatty acid is less specific for palmitate than it was thought ea rlier and that other saturated, mono- and even polyunsaturated long ch ain fatty acids can also participate. The chain length and the extent of unsaturation of the protein-linked fatty acid moiety can, very like ly, modulate hydrophobic protein-membrane lipid and protein-protein in teractions. CD9, HLA class I glycoprotein, glycoproteins Ib, IX and IV , P-selectin and a subunits of G proteins have been demonstrated unequ ivocally as S-fatty acid acylated platelet proteins.