Xin repeats define a novel actin-binding motif
Xin repeats define a novel actin-binding motif
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DOI：
10.1242/jcs.01406
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发表时间：
2004-10-15
影响因子：
4
通讯作者：
van der Ven, PFM
中科院分区：
文献类型：
--
作者：
Pacholsky, D;Vakeel, P;van der Ven, PFM
Xin 是一种在心肌和骨骼肌早期发育阶段表达的蛋白质。免疫定位研究表明，Xin 在胚胎小鼠心脏中存在外周定位，其中 β-连环蛋白和 N-钙粘蛋白位于其中。在成人组织中，Xin 主要存在于心肌细胞的闰盘和骨骼肌细胞的肌腱连接处，这两个部位都是肌原纤维末端与肌膜的专门附着位点。 Xin 蛋白的很大一部分由功能未知的独特 16 个氨基酸重复组成。我们通过转染实验和肌动蛋白结合测定研究了 Xin 重复序列的特征，并确定在培养细胞中表达后，这些重复序列结合并稳定基于肌动蛋白的细胞骨架。与骨骼肌肌动蛋白的体外共沉淀试验表明，它们不仅直接结合肌动蛋白丝，而且具有将微丝排列成网络的能力，并在低速离心时沉淀。在 Xin 重复蛋白 2' (XIRP2) 中也发现了非常相似的重复，这是一种似乎主要在横纹肌中表达的新型蛋白。人 XIRP2 包含 28 个 Xin 重复序列，其特性与 Xin 相同。我们得出的结论是，Xin 重复序列定义了一种新的、重复的肌动蛋白结合基序，存在于至少两种不同的肌肉蛋白中。因此，这些 Xin 重复蛋白构成了肌动蛋白结合蛋白新家族的前两个成员。
Xin is a protein that is expressed during early developmental stages of cardiac and skeletal muscles. Immunolocalization studies indicated a peripheral localization in embryonic mouse heart, where Xin localizes with beta-catenin and N-cadherin. In adult tissues, Xin is found primarily in the intercalated discs of cardiomyocytes and the myotendinous junctions of skeletal muscle cells, both specialized attachment sites of the myofibrillar ends to the sarcolemma. A large part of the Xin protein consists of unique 16 amino acid repeats with unknown function. We have investigated the characteristics of the Xin repeats by transfection experiments and actin-binding assays and ascertained that, upon expression in cultured cells, these repeats bind to and stabilize the actin-based cytoskeleton. In vitro co-sedimentation assays with skeletal muscle actin indicated that they not only directly bind actin filaments, but also have the capability of arranging microfilaments into networks that sediment upon low-speed centrifugation. Very similar repeats were also found in Xin-repeat protein 2' (XIRP2), a novel protein that seems to be expressed mainly in striated muscles. Human XIRP2 contains 28 Xin repeats with properties identical to those of Xin. We conclude that the Xin repeats define a novel, repetitive actin-binding motif present in at least two different muscle proteins. These Xin-repeat proteins therefore constitute the first two members of a novel family of actin-binding proteins.