DETERMINATION OF N-TERMINAL MYRISTOYLATION OF PROTEINS USING A COMBINED GAS-CHROMATOGRAPHIC MASS-SPECTROMETRIC ASSAY OF DERIVED MYRISTOYLGLYCINE - ELECTRON IMPACT-INDUCED FRAGMENTATION OF ACYLGLYCINE DERIVATIVES

A method based on gas chromatography/mass spectrometry is described fo r the detection of N-terminal myristoylation of proteins. Myristoylgly cine, derivatized as its trimethylsily (TMS) ester, gave an electron i mpact mass spectrum containing abundant molecular and [M - CH3](+) ion s, together with several lolls diagnostic of the acyl glycine moiety, namely at m/z 145, 158, 172 and 189. The compositions of these ions an d the mechanisms that produced them were investigated by high-resoluti on mass measurements, deuterium labelling and the preparation of analo gous compounds. As these ions were present in the spectra of all acylg lycines examined, they could be used as markers for these compounds. A selected-ion monitoring method for the detection of myristoylglycine was set ap using the above ions and was used to confirm the presence o f N-terminal myristoylation in three reference peptides. A series of i ons produced by radical-induced cleavage of the alkyl chain following TMS group migration and elimination of carbon dioxide gave information on the structure of the chain and could be used to determine the stru cture of other potential acylglycines such as those with unsaturated a cyl chains. Thus the derivatives could be used not only to detect myri stoylation of protein, but also to detect and determine tbe structures of other acyl substituents.