Purification and characterization of yeast myristoyl CoA:protein N-myristoyltransferase

D. A. Towler, S. P. Adams, S. R. Eubanks, D. S. Towery, E. Jackson-Machelski, L. Glaser, J. I. Gordon

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Abstract

Myristoyl CoA:protein N-myristolytransferase (NMT) catalyzes the addition of myristic acid to the amino-terminal glycine residues of a number of eukaryotic proteins. Recently, we developed a cell-free system for analyzing NMT activity and have begun to characterize the substrate specificity of this enzyme by using a series of synthetic peptides. We have now purified NMT from Saccharomyces cerevisiae to apparent homogeneity. The native enzyme is a 55-kDa protein, exhibits no requirement for divalent cation, and appears to contain a histidine residue critical for enzyme activity. A total of 42 synthetic peptides have been used to define structure/activity relationships in NMT substrates. An amino-terminal glycine is required for acylation; substitution with glycine analogues produces peptides that are inactive as substrates or inhibitors of NMT. A broad spectrum of amino acids is permitted at positions 3 and 4, while strict amino acid requirements are exhibited at position 5. Replacement of Ala5 in the peptide Gys-Asn-Ala-Ala-Ala-Arg-Arg with Asp ablates the peptide's myristoyl-accepting activity. A serine at this position results in a decrease by a factor of ≃ 500 in the apparent K(m) in the context of three different sequences. Penta- and hexa-peptides are substrates, but with decreased affinity. These studies establish that structural information important for NMT-ligand interaction exists beyond the first two amino acids in peptide substrates and that the side chains of residue 5 play a critical role in the binding of substrates to this enzyme.

Original languageEnglish (US)
Pages (from-to)2708-2712
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume84
Issue number9
DOIs
StatePublished - Jun 25 1987

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