Arabidopsis capping protein (AtCP) is a heterodimer that regulates assembly at the barbed ends of actin filaments
Arabidopsis capping protein (AtCP) is a heterodimer that regulates assembly at the barbed ends of actin filaments
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DOI：
10.1074/jbc.m306670200
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发表时间：
2003-11-07
影响因子：
4.8
通讯作者：
Staiger, CJ
中科院分区：
文献类型：
--
作者：
Huang, SJ;Blanchoin, L;Staiger, CJ
肌动蛋白丝聚合和解聚的精确调节对于许多细胞过程是必不可少的，并且由许多肌动蛋白结合蛋白（ABP）编排。在高等植物中，特征良好的ABPs的数量是相当有限的，一些证据表明，明显保守的蛋白质的生化特性的显着差异。在这里，我们提供了第一个证据的存在和生化特性的异二聚体帽蛋白从拟南芥（AtCP）。纯化的重组蛋白结合到肌动蛋白丝倒刺末端，如动力学和稳态下测定的，K-d值为12-24 nM。AtCP防止在接种延伸反应期间将profilin肌动蛋白添加到倒刺末端，并抑制稀释介导的解聚。然而，它不切断肌动蛋白丝，对肌动蛋白的来源没有偏好。在从Mg-ATP-肌动蛋白单体组装的过程中，AtCP消除了肌动蛋白聚合的初始滞后期，并增加了聚合的最大速率。事实上，每个AtCP多肽产生的0.042个尖端的肌动蛋白成核效率与小鼠CapZ相比是有利的，小鼠CapZ具有每个CapZ多肽0.17个尖端的最大成核。AtCP活性不受钙的影响，但对磷脂酰肌醇4，5-二磷酸敏感。我们认为AtCP是植物细胞中肌动蛋白动力学的主要调节因子，与丰富的profilin一起，负责维持大量的肌动蛋白亚基和令人惊讶的小群体的F-肌动蛋白。
The precise regulation of actin filament polymerization and depolymerization is essential for many cellular processes and is choreographed by a multitude of actin-binding proteins (ABPs). In higher plants the number of well characterized ABPs is quite limited, and some evidence points to significant differences in the biochemical properties of apparently conserved proteins. Here we provide the first evidence for the existence and biochemical properties of a heterodimeric capping protein from Arabidopsis thaliana (AtCP). The purified recombinant protein binds to actin filament barbed ends with K-d values of 12-24 nM, as assayed both kinetically and at steady state. AtCP prevents the addition of profilin actin to barbed ends during a seeded elongation reaction and suppresses dilution-mediated depolymerization. It does not, however, sever actin filaments and does not have a preference for the source of actin. During assembly from Mg-ATP-actin monomers, AtCP eliminates the initial lag period for actin polymerization and increases the maximum rate of polymerization. Indeed, the efficiency of actin nucleation of 0.042 pointed ends created per AtCP polypeptide compares favorably with mouse CapZ, which has a maximal nucleation of 0.17 pointed ends per CapZ polypeptide. AtCP activity is not affected by calcium but is sensitive to phosphatidylinositol 4,5-bisphosphate. We propose that AtCP is a major regulator of actin dynamics in plant cells that, together with abundant profilin, is responsible for maintaining a large pool of actin subunits and a surprisingly small population of F-actin.