Department of Horticulture, Plant Physiology/Biochemistry/Molecular Biology Program, University of Kentucky, Lexington, Kentucky 40546, USA.
Nat Commun. 2010 Jul 27;1:43. doi: 10.1038/ncomms1044.
Calmodulin (CaM) is a key mediator of calcium-dependent signalling and is subject to regulatory post-translational modifications, including trimethylation of Lys-115. In this paper, we identify a class I, non-SET domain protein methyltransferase, calmodulin-lysine N-methyltransferase (EC 2.1.1.60). A polypeptide chosen from a fraction enriched in calmodulin methyltransferase activity was trypsinized and analysed by tandem mass spectrometry. The amino-acid sequence obtained identified conserved, homologous proteins of unknown function across a wide range of species, thus implicating a broad role for lysine methylation in calcium-dependent signalling. Encoded by c2orf34, the human homologue is a component of two related multigene deletion syndromes in humans. Human, rat, frog, insect and plant homologues were cloned and Escherichia coli-recombinant proteins catalysed the formation of a trimethyllysyl residue at position 115 in CaM, as verified by product analyses and mass spectrometry.
钙调蛋白（CaM）是钙依赖性信号转导的关键介质，并且受到调节性翻译后修饰的影响，包括赖氨酸 115 的三甲基化。在本文中，我们鉴定了一类 I 型、非 SET 域蛋白甲基转移酶，即钙调蛋白-赖氨酸 N-甲基转移酶（EC 2.1.1.60）。从富含钙调蛋白甲基转移酶活性的级分中选择的多肽经胰蛋白酶消化后，通过串联质谱分析。获得的氨基酸序列鉴定了具有未知功能的保守同源蛋白，跨越了广泛的物种范围，从而暗示了赖氨酸甲基化在钙依赖性信号转导中的广泛作用。由 c2orf34 编码的人类同源物是人类两种相关的多基因缺失综合征的组成部分。克隆了人、大鼠、青蛙、昆虫和植物的同源物，并通过产物分析和质谱证实了大肠杆菌重组蛋白在 CaM 的第 115 位催化形成三甲基赖氨酸残基。
