title: N-myristoylation of p60src. Identification of a myristoyl-CoA:glycylpeptide N-myristoyltransferase in rat tissues.
abstract: A 16-residue synthetic peptide corresponding to the N-terminal sequence of p60src was used as the acyl acceptor in an assay for myristoyl-CoA:glycylpeptide N-myristoyltransferase in rat tissues. An additional C-terminal tyrosine amide was added to this peptide to facilitate radioiodination and enhance detectability. Reverse-phase h.p.l.c. enabled the simultaneous detection and quantification of the peptide substrate and its N-myristoylated product. N-Myristoyltransferase activity was highest in the brain with decreasing activities in lung, small intestine, kidney, heart, skeletal muscle and liver. Brain activity was distributed approximately equally between the 100,000 g pellet and supernatant fractions. The soluble enzyme exhibited a Kappm of 20 microM for the src peptide and an optimum between pH 7.0 and 7.5. Maximum N-acylating activity was seen with myristoyl (C14:0)-CoA with lower activities found with the C10:0-CoA and C12:0-CoA homologues. No activity was obtained with palmitoyl (C18:0)-CoA but this derivative inhibited N-myristoyltransferase activity greater than 50% at equimolar concentrations with myristoyl-CoA. With a decapeptide corresponding to the N-terminal sequence of the cyclic AMP-dependent protein kinase catalytic subunit as the acyl acceptor, the brain enzyme displayed a Kapp.m of 117 microM and was about 14-fold less catalytically effective than with the p60src acyl acceptor. Transferase activity was also seen with a 16-residue peptide corresponding to the N-terminal sequence of the HIV p17gag structural protein. Inhibition studies with shorter src peptide analogues indicated an enzyme specificity for the p60src acyl acceptor beyond 9 residues.
mesh_terms: D000217:Acyltransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D007700:Kinetics; D008297:Male; D015688:Oncogene Protein pp60(v-src); D010455:Peptides / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012191:Retroviridae Proteins / Q000378:metabolism*; D013379:Substrate Specificity; D014018:Tissue Distribution
chemical_list: D010455:Peptides; D012191:Retroviridae Proteins; D000217:Acyltransferases; C050480:glycylpeptide N-tetradecanoyltransferase; D011505:Protein-Tyrosine Kinases; D015688:Oncogene Protein pp60(v-src)