Zelicof A, Protopopov V, David D, Lin X Y, Lustgarten V, Gerst J E
Department of Cell Biology and Anatomy, Mount Sinai School of Medicine, New York, New York 10029, USA.
J Biol Chem. 1996 Jul 26;271(30):18243-52. doi: 10.1074/jbc.271.30.18243.
The yeast adenylyl cyclase-associated protein, CAP, was identified as a component of the RAS-activated cyclase complex. CAP consists of two functional domains separated by a proline-rich region. One domain, which localizes to the amino terminus, mediates RAS signaling through adenylyl cyclase, while a domain at the carboxyl terminus is involved in the regulation of cell growth and morphogenesis. Recently, the carboxyl terminus of yeast CAP was shown to sequester actin, but whether this function has been conserved, and is the sole function of this domain, is unclear. Here, we demonstrate that the carboxyl-terminal domains of CAP and CAP homologs have two separate functions. We show that carboxyl-terminals of both yeast CAP and a mammalian CAP homolog, MCH1, bind to actin. We also show that this domain contains a signal for dimerization, allowing both CAP and MCH1 to form homodimers and heterodimers. The properties of actin binding and dimerization are mediated by separate regions on the carboxyl terminus; the last 27 amino acids of CAP being critical for actin binding. Finally, we present evidence that links a segment of the proline-rich region of CAP to its localization in yeast. Together, these results suggest that all three domains of CAP proteins are functional.
酵母腺苷酸环化酶相关蛋白（CAP）被鉴定为RAS激活的环化酶复合物的一个组成部分。CAP由两个功能结构域组成，中间被一个富含脯氨酸的区域隔开。一个位于氨基末端的结构域通过腺苷酸环化酶介导RAS信号传导，而羧基末端的一个结构域则参与细胞生长和形态发生的调控。最近，酵母CAP的羧基末端被证明能隔离肌动蛋白，但这种功能是否保守，以及是否是该结构域的唯一功能，尚不清楚。在这里，我们证明了CAP及其同源物的羧基末端结构域具有两种不同的功能。我们发现酵母CAP和一种哺乳动物CAP同源物MCH1的羧基末端都能与肌动蛋白结合。我们还表明，该结构域包含一个二聚化信号，使CAP和MCH1都能形成同二聚体和异二聚体。肌动蛋白结合和二聚化的特性由羧基末端的不同区域介导；CAP的最后27个氨基酸对肌动蛋白结合至关重要。最后，我们提供的证据将CAP富含脯氨酸区域的一段与它在酵母中的定位联系起来。总之，这些结果表明CAP蛋白的所有三个结构域都具有功能。
