11-(ethylthio)undecanoic acid. A myristic acid analogue of altered hydrophobicity which is functional for peptide N-myristoylation with wheat germ and yeast acyltransferase

The covalent attachment of myristic acid to the NH₂-terminal glycine residue of proteins is catalyzed by the enzyme myristoyl CoA:protein N-myristoyltransferase (NMT). Using synthetic octapeptide substrates we have identified and characterized an NMT activity in wheat germ lysates used for cell-free translation of exogenous mRNAs. C-12 and C-14 fatty acids are efficiently transferred to the peptides by this plant NMT, but C-10 and C-16 fatty acids are not. Glycine is required as the NH₂-terminal residue: peptides with an NH₂-terminal alanine were not substrates. Peptides with proline, aspartic acid, or tyrosine residues adjacent to the NH₂-terminal glycine were also not myristoylated. Serine in the fifth position reduced the peptide's K(m) up to 4000-fold. We have chemically synthesized a sulfur analogue of myristate, 11-(ethylthio)undecanoic acid. Its CoA ester is as good a substrate as myristoyl-CoA for both wheat germ and yeast NMT. Peptides linked to 11-(ethylthio)undecanoic acid are less hydrophobic than the corresponding myristoylpeptides. 11-(Ethylthio)undecanoic acid may, therefore, help define the role of myristic acid in targeting of acyl proteins within cells.