Pennestri Matteo, Melino Sonia, Contessa Gian Marco, Casavola Elena Caroli, Paci Maurizio, Ragnini-Wilson Antonella, Cicero Daniel O
Department of Chemical Science and Technology, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy.
J Biol Chem. 2007 Jan 5;282(1):667-79. doi: 10.1074/jbc.M607016200. Epub 2006 Oct 29.
Calmodulin, regulatory, and essential myosin light chain are evolutionary conserved proteins that, by binding to IQ motifs of target proteins, regulate essential intracellular processes among which are efficiency of secretory vesicles release at synapsis, intracellular signaling, and regulation of cell division. The yeast Saccharomyces cerevisiae calmodulin Cmd1 and the essential myosin light chain Mlc1p share the ability to interact with the class V myosin Myo2p and Myo4 and the class II myosin Myo1p. These myosins are required for vesicle, organelle, and mRNA transport, spindle orientation, and cytokinesis. We have used the budding yeast model system to study how calmodulin and essential myosin light chain selectively regulate class V myosin function. NMR structural analysis of uncomplexed Mlc1p and interaction studies with the first three IQ motifs of Myo2p show that the structural similarities between Mlc1p and the other members of the EF-hand superfamily of calmodulin-like proteins are mainly restricted to the C-lobe of these proteins. The N-lobe of Mlc1p presents a significantly compact and stable structure that is maintained both in the free and complexed states. The Mlc1p N-lobe interacts with the IQ motif in a manner that is regulated both by the IQ motifs sequence as well as by light chain structural features. These characteristic allows a distinctive interaction of Mlc1p with the first IQ motif of Myo2p when compared with calmodulin. This finding gives us a novel view of how calmodulin and essential light chain, through a differential binding to IQ1 of class V myosin motor, regulate this activity during vegetative growth and cytokinesis.
钙调蛋白、调节性和必需的肌球蛋白轻链是进化上保守的蛋白质，它们通过与靶蛋白的IQ基序结合，调节细胞内的基本过程，其中包括突触处分泌囊泡释放的效率、细胞内信号传导以及细胞分裂的调节。酿酒酵母钙调蛋白Cmd1和必需的肌球蛋白轻链Mlc1p具有与V类肌球蛋白Myo2p和Myo4以及II类肌球蛋白Myo1p相互作用的能力。这些肌球蛋白是囊泡、细胞器和mRNA运输、纺锤体定向和胞质分裂所必需的。我们利用芽殖酵母模型系统研究钙调蛋白和必需的肌球蛋白轻链如何选择性地调节V类肌球蛋白的功能。未结合的Mlc1p的核磁共振结构分析以及与Myo2p的前三个IQ基序的相互作用研究表明，Mlc1p与钙调蛋白样蛋白的EF手超家族的其他成员之间的结构相似性主要局限于这些蛋白质的C叶。Mlc1p的N叶呈现出显著紧凑和稳定的结构，在游离和结合状态下均保持不变。Mlc1p的N叶以一种受IQ基序序列以及轻链结构特征调节的方式与IQ基序相互作用。与钙调蛋白相比，这些特征使得Mlc1p与Myo2p的第一个IQ基序具有独特的相互作用。这一发现为钙调蛋白和必需轻链如何通过与V类肌球蛋白马达的IQ1的差异结合，在营养生长和胞质分裂过程中调节这种活性提供了新的视角。
