Identification of the single specific IQ motif of myosin V from which calmodulin dissociates in the presence of Ca2+
Identification of the single specific IQ motif of myosin V from which calmodulin dissociates in the presence of Ca2+
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DOI：
10.1021/bi0613877
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发表时间：
2006-09-26
期刊：
影响因子：
2.9
通讯作者：
Ando, Toshio
中科院分区：
文献类型：
--
作者：
Koide, Hiroshi;Kinoshita, Tatsuya;Ando, Toshio
鸡脑肌球蛋白V(BMV)的每个重链都有一个由6个不同氨基酸序列的IQ基序组成的颈区。这六个IQ基序形成了五个钙调蛋白(CaM)分子和一个基本轻链(17或23 kDa)的结合位点。当钙浓度较高时，总共10个CaM分子中的一小部分从BMV的一个分子中解离，导致基于肌动蛋白的马达活性丧失。在低钙浓度下，两个外源CaM分子与一个CaM释放的BMV分子结合。这表明，钙诱导的CaM解离只有一个特定的智商基序。在本研究中，我们将特定的IQ基序确定为IQ2，这是从Neck结构域的N末端计数时的第二个IQ基序。此外，我们还证明了必需的轻链并不位于IQ1和IQ2上。这些发现来自于BMV在高钙浓度下的蛋白分解，特别是在颈部，并对消化进行了SDS-PAGE分析。
Each heavy chain of dimeric chick brain myosin V (BMV) has a neck domain consisting of six IQ motifs with different amino acid sequences. The six IQ motifs form binding sites for five calmodulin (CaM) molecules and one essential light chain (either 17 or 23 kDa). When the calcium concentration is high, a small fraction of the 10 total CaM molecules dissociates from one molecule of BMV, resulting in loss of actin-based motor activity. At low Ca2+ concentrations, two molecules of exogenous CaM associate with one molecule of CaM-released BMV. This suggests that there is a single specific IQ motif responsible for the calcium-induced dissociation of CaM. In this study, we identify the specific IQ motif to be IQ2, the second IQ motif when counted from the N-terminal end of the neck domain. In addition, we showed that the essential light chains do not reside on IQ1 and IQ2. These findings were derived from proteolysis of BMV at high Ca2+ concentrations specifically at the neck region and SDS-PAGE analyses of the digests.