Kinetic and structural evidence for a sequential ordered Bi Bi mechanism of catalysis by Saccharomyces cerevisiae myristoyl-CoA:protein N-myristoyltransferase

Abstract

The mechanism of catalysis of Escherichia coli-derived Saccharomyces cerevisiae myristoyl-CoA: protein N-myristoyltransferase (NMT) has been characterized. Previous studies indicated that a high affinity reaction intermediate forms between NMT and myristoyl-CoA in the absence of a peptide substrate. This complex has been further characterized using S-(2-oxo)pentadecyl-CoA, a nonhydrolyzable myristoyl-CoA analog. Binding studies involving this analog, as well as myristoylpeptide and CoA, have indicated that the CoA moiety of the acyl substrate is retained in the acyl-NMT complex prior to peptide addition. These structural data, along with kinetic studies of myristoylpeptide and CoA product inhibition, indicate that the mechanism of catalysis of NMT is ordered Bi Bi, with myristoyl-CoA binding to NMT occurring prior to peptide binding and CoA release taking place before release of acyl peptide. Further analyses of the interactions between NMT, acyl peptide, and CoA demonstrate that NMT is able to deacylate a myristoylpeptide in the presence of CoA.