Role of the C-terminal SH3 domain and N-terminal tyrosine phosphorylation in regulation of Tim and related Dbl-family proteins.
Role of the C-terminal SH3 domain and N-terminal tyrosine phosphorylation in regulation of Tim and related Dbl-family proteins.
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DOI：
10.1021/bi702543p
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发表时间：
2008-07
期刊：
影响因子：
2.9
通讯作者：
M. Yohe;K. Rossman;J. Sondek
中科院分区：
文献类型：
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作者：
M. Yohe;K. Rossman;J. Sondek
Dbl相关癌蛋白是Rho家族GTP酶特异性的鸟嘌呤核苷酸交换因子（GEF），并且通常具有串联Dbl（DH）和普列克底物蛋白同源（PH）结构域，其协同作用以催化交换。虽然许多Dbl家族蛋白的交换潜力是由截短组成型激活的，但许多Dbl家族蛋白的精确调节机制尚不清楚。Tim和Vav是类似调节的远亲Dbl家族蛋白;它们的Dbl同源（DH）结构域与N-末端螺旋相互作用以排除和防止Rho GTP酶的活化。阻断螺旋的磷酸化、取代或缺失可缓解这种自身抑制。在这里，我们表明，其他两个DBL家族蛋白质，NGEF和WGEF，其中像蒂姆包含一个C-末端SH 3结构域，也被激活的酪氨酸磷酸化的阻断螺旋。因此，通过使用短的N-末端螺旋的直接空间排阻的DH结构域的基础自身抑制可能代表Dbl相关蛋白的大家族的保守调节机制。许多其他Dbl家族GEF的N端截短或磷酸化导致其活化;类似的自抑制机制可以解释其中一些事件。此外，我们表明，C-末端SH 3结构域结合到聚脯氨酸区域N-末端的DH结构域的蒂姆亚组的Dbl-家族蛋白提供了一个独特的机制，调节自动抑制的交换活性，在功能上连接到自动抑制螺旋和DH结构域之间的相互作用。
Dbl-related oncoproteins are guanine nucleotide exchange factors (GEFs) specific for Rho-family GTPases and typically possess tandem Dbl (DH) and pleckstrin homology (PH) domains that act in concert to catalyze exchange. Although the exchange potential of many Dbl-family proteins is constitutively activated by truncation, the precise mechanisms of regulation for many Dbl-family proteins are unknown. Tim and Vav are distantly related Dbl-family proteins that are similarly regulated; their Dbl homology (DH) domains interact with N-terminal helices to exclude and prevent activation of Rho GTPases. Phosphorylation, substitution, or deletion of the blocking helices relieves this autoinhibition. Here we show that two other Dbl-family proteins, Ngef and Wgef, which like Tim contain a C-terminal SH3 domain, are also activated by tyrosine phosphorylation of a blocking helix. Consequently, basal autoinhibition of DH domains by direct steric exclusion using short N-terminal helices likely represents a conserved mechanism of regulation for the large family of Dbl-related proteins. N-Terminal truncation or phosphorylation of many other Dbl-family GEFs leads to their activation; similar autoinhibition mechanisms could explain some of these events. In addition, we show that the C-terminal SH3 domain binding to a polyproline region N-terminal to the DH domain of the Tim subgroup of Dbl-family proteins provides a unique mechanism of regulated autoinhibition of exchange activity that is functionally linked to the interactions between the autoinhibitory helix and the DH domain.