Vijayasarathy C, Rao B S
Biochim Biophys Acta. 1987 Jan 20;923(1):156-65. doi: 10.1016/0304-4165(87)90139-5.
A new class of protein methylase (S-adenosylmethionine:protein-histidine N-methyltransferase) which methylates histidine residues of protein substrates using S-adenosylmethionine as the methyl donor has been partially purified from rabbit skeletal muscle, 22-fold with a yield of 56%. The enzyme activity was monitored using denatured myofibrils from young rabbit skeletal muscle as the methyl acceptor protein substrate. The enzyme was localised in the myofibrillar fraction and myofibrils isolated in pure form represented the enzyme-substrate complex. The enzyme was solubilised in 0.275 M KCl. The methylase showed no requirement for any metal ion and has a pH optimum of 8.0. It was shown to require a reducing agent like mercaptoethanol for its activity. It was also shown that cardiac and skeletal muscle forms of actins obtained from different species serve as the efficient methyl acceptor protein substrates. Since the enzyme was found to methylate specifically the histidine residues of actin we propose to designate this new methylase as protein methylase IV, to distinguish it from the already known protein methylases I, II and III.
一类新的蛋白质甲基化酶（S-腺苷甲硫氨酸：蛋白质-组氨酸N-甲基转移酶）已从兔骨骼肌中部分纯化，该酶以S-腺苷甲硫氨酸作为甲基供体，使蛋白质底物的组氨酸残基甲基化，纯化了22倍，产率为56%。使用来自幼兔骨骼肌的变性肌原纤维作为甲基受体蛋白质底物来监测酶活性。该酶定位于肌原纤维部分，以纯形式分离的肌原纤维代表酶-底物复合物。该酶可溶于0.275M KCl中。这种甲基化酶不需要任何金属离子，最适pH为8.0。已证明其活性需要像巯基乙醇这样的还原剂。还表明，从不同物种获得的心肌和骨骼肌形式的肌动蛋白可作为有效的甲基受体蛋白质底物。由于发现该酶特异性地使肌动蛋白的组氨酸残基甲基化，我们建议将这种新的甲基化酶命名为蛋白质甲基化酶IV，以区别于已知的蛋白质甲基化酶I、II和III。
