title: In vivo carboxyl methylation of human eruthrocyte membrane proteins.
abstract: In order to study the in vivo methylation of ghost membrane proteins, human erythrocytes were incubated with L-[methyl-3H]methionine. The [3H]methyl incorporation into the membrane components was observed in freshly prepared erythrocytes. Upon treatment of the methylated membrane at pH 7.4, 100 degrees C for 5 min, a condition which is known to hydrolyze protein-carboxyl methyl ester, 80% of the incorporated [3H]methyl was recovered as methanol. Cycloleucine, an inhibitor for S-adenosylmethionine synthetase, inhibited 70% of the methylation. The analyses of the methylated proteins by sodium dodecyl sulfate/polyacrylamide gel electrophoresis revealed two major methylated protein peaks which were tentatively identified as glycophorin A and band 4.5. This methylation pattern is similar to the in vitro methylation pattern when purified human ghosts were methylated with purified protein methylase II and S-adenosylmethionine (Galletti, P., Paik, W. K., and Kim, S. (1979) Eur. J. Biochem. 97, 221-227). It is concluded that carboxyl methylation of erythrocyte membrane proteins is the major methylation reaction in vivo in these membranes.
mesh_terms: D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000097:blood*; D008715:Methionine / Q000097:blood; D008745:Methylation; D011691:Puromycin / Q000494:pharmacology; D012436:S-Adenosylmethionine / Q000097:blood
chemical_list: D008565:Membrane Proteins; D011691:Puromycin; D012436:S-Adenosylmethionine; D008715:Methionine