Substrate Specificity of Mammalian N-Terminal 伪-Amino Methyltransferase NRMT

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• 作者：Janusz J. Petkowski ; Christine E. Schaner Tooley ; Lissa C. Anderson ; Igor A. Shumilin ; Jeremy L. Balsbaugh ; Jeffrey Shabanowitz ; Donald F. Hunt ; Wladek Minor ; Ian G. Macara
• 刊名：Biochemistry
• 出版年：2012
• 出版时间：July 31, 2012
• 年：2012
• 卷：51
• 期：30
• 页码：5942-5950
• 全文大小：412K
• 年卷期：v.51,no.30(July 31, 2012)
• ISSN：1520-4995

文摘

N-Terminal methylation of free 伪-amino groups is a post-translational modification of proteins that was first described 30 years ago but has been studied very little. In this modification, the initiating M residue is cleaved and the exposed 伪-amino group is mono-, di-, or trimethylated by NRMT, a recently identified N-terminal methyltransferase. Currently, all known eukaryotic 伪-amino-methylated proteins have a unique N-terminal motif, M-X-P-K, where X is A, P, or S. NRMT can also methylate artificial substrates in vitro in which X is G, F, Y, C, M, K, R, N, Q, or H. Methylation efficiencies of N-terminal amino acids are variable with respect to the identity of X. Here we use in vitro peptide methylation assays and substrate immunoprecipitations to show that the canonical M-X-P-K methylation motif is not the only one recognized by NRMT. We predict that N-terminal methylation is a widespread post-translational modification and that there is interplay between N-terminal acetylation and N-terminal methylation. We also use isothermal calorimetry experiments to demonstrate that NRMT can efficiently recognize and bind to its fully methylated products.