EZRIN SELF-ASSOCIATION INVOLVES BINDING OF AN N-TERMINAL DOMAIN TO A NORMALLY MASKED C-TERMINAL DOMAIN THAT INCLUDES THE F-ACTIN BINDING-SITE
EZRIN SELF-ASSOCIATION INVOLVES BINDING OF AN N-TERMINAL DOMAIN TO A NORMALLY MASKED C-TERMINAL DOMAIN THAT INCLUDES THE F-ACTIN BINDING-SITE
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DOI：
10.1091/mbc.6.8.1061
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发表时间：
1995-08-01
影响因子：
3.3
通讯作者：
BRETSCHER, A
中科院分区：
文献类型：
--
作者：
GARY, R;BRETSCHER, A
Ezrin是一种膜-细胞骨架连接蛋白，其集中在富含肌动蛋白的表面结构中。它与微绒毛蛋白radixin和moesin以及肿瘤抑制因子merlin/schwannomin密切相关。细胞提取物含有埃兹蛋白二聚体和埃兹蛋白-膜突蛋白异源二聚体。通过印迹覆盖测定截短的埃兹蛋白融合蛋白以确定哪些区域介导自缔合。在这里，我们报告说，埃兹蛋白自我协会发生的头到尾加入不同的N-末端和C-末端结构域。这是可能的，这些结构域，称为N-和C-ERMAD（ezrin-radixin-moesin关联结构域），负责ERM家族成员之间的同型和异型协会。ezrin的N-ERMAD位于氨基酸1-296内;缺失另外10个残基导致活性丧失。C-ERMAD定位于埃兹蛋白的最后107个氨基酸，残基479-585。C端的两个残基是活性所需的，530-585的区域是不够的。在天然单体中掩蔽C-ERMAD。暴露这个域需要展开ezrin与十二烷基硫酸钠或expressin，g域作为截短蛋白的一部分。除非C-ERMAD能够接近其N-末端伴侣，否则分子间缔合不会发生。可以推断，体内二聚化需要暴露该掩蔽结构域的活化步骤。构象上不可接近的C-末端区域包括F-肌动蛋白结合位点，这表明这种活性同样受到掩蔽的调节。
Ezrin is a membrane-cytoskeletal linking protein that is concentrated in actin-rich surface structures. It is closely related to the microvillar proteins radixin and moesin and to the tumor suppressor merlin/schwannomin. Cell extracts contain ezrin dimers and ezrin-moesin heterodimers in addition to monomers. Truncated ezrin fusion proteins were assayed by blot overlay to determine which regions mediate self-association. Here we report that ezrin self-association occurs by head-to-tail joining of distinct N-terminal and C-terminal domains. It is likely that these domains, termed N- and C-ERMADs (ezrin-radixin-moesin association domain), are responsible for homotypic and heterotypic associations among ERM family members. The N-ERMAD of ezrin resided within amino acids 1-296; deletion of 10 additional residues resulted in loss of activity. The C-ERMAD was mapped to the last 107 amino acids of ezrin, residues 479-585. The two residues at the C-terminus were required for activity, and the region from 530-585 was insufficient. The C-ERMAD was masked in the native monomer. Exposure of this domain required unfolding ezrin with sodium dodecyl sulfate or expressin,g the domain as part of a truncated protein. Intermolecular association could not occur unless the C-ERMAD had been made accessible to its N-terminal partner. It can be inferred that dimerization in vivo requires an activation step that exposes this masked domain. The conformationally inaccessible C-terminal region included the F-actin binding site, suggesting that this activity is likewise regulated by masking.