Palmitoylation of membrane proteins inSpiroplasma floricola

Abstract

Covalent modification ofSpiroplasma floricola membrane proteins by fatty acids was determined by in vivo labeling of the cells with radioactive fatty acids followed by separation on one-dimensional SDS-polyacrylamide gels and visualization by autoradiography. Approximately 25 different proteins were found to be labeled with [³H]-palmitate, whereas almost none were labeled with [³H]-oleate. The radioactivity could not be removed from the palmitoylated membrane proteins by boiling in SDS or by exhaustive extraction with chloroform-methanol (2∶1). Nevertheless, treating the palmitoylated proteins with a 0.1N KOH solution removed approximately 70% of the bound [³H]-palmitate. The major protein-bound fatty acid species were identified, following their release from the protein by chemical cleavage, as palmitic acid and stearic acid (83% and 7.5%, respectively).