Characterization of alkylamine-sensitive site in alpha 2-macroglobulin.
Characterization of alkylamine-sensitive site in alpha 2-macroglobulin.
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α2-巨球蛋白中烷基胺敏感位点的表征。
DOI：
10.1073/pnas.76.9.4313
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发表时间：
1979
影响因子：
11.1
通讯作者：
J. Howard
中科院分区：
文献类型：
--
作者：
R. Swenson;J. Howard
甲胺与血浆蛋白酶抑制剂α 2-巨球蛋白反应，形成不可逆的共价修饰。反应定量表明，每个天然四聚体蛋白（Mr = 725,000）有3.9 +/- (SD) 0.4个反应位点，或每个亚基有一个位点。该反应具有选择性和特异性，因为在由[14C]甲胺处理的α - 2巨球蛋白衍生的肽图的放射自显影上只观察到1或2个标记肽。从所标记的蛋白中分离出单个胰凝乳肽，总产率为56%。经Edman降解的肽序列为Gly-Cys-Gly-Glu-X-Asn-Met-(Val, Leu)，其中X是唯一放射性标记的苯硫代海因衍生物。氨基酸分析和质谱分析表明X为γ -谷氨酰基甲基酰胺。由于谷氨酸和谷氨酰胺残基通常不与烷基胺反应，这项工作提出了在选定的蛋白质中存在替代活化中心的推定证据。
Methylamine reacts with the plasma protease inhibitor, alpha 2-macroglobulin, to form an irreversible, covalent modification. Quantitation of the reaction indicates 3.9 +/- (SD) 0.4 reactive sites per native tetrameric protein (Mr = 725,000) or one site per subunit. The reaction is selective and specific in that only 1 or 2 labeled peptides are observed on radioautography of peptide maps derived from [14C]methylamine-treated alpha 2-macroglobulin. A single chymotryptic peptide was isolated in 56% overall yield from the labeled protein. The peptide sequence by Edman degradation was found to be Gly-Cys-Gly-Glu-X-Asn-Met-(Val, Leu), in which X was the only radiolabeled phenylthiohydantoin derivative. Amino acid analysis and mass spectral analysis of the derivative suggests that X is gamma-glutamylmethylamide. Because glutamic acid and glutamine residues do not normally react with alkylamines, this work presents presumptive evidence for an alternative activated center in selected proteins.