GAP1 family members constitute bifunctional Ras and Rap GTPase-activating proteins
GAP1 family members constitute bifunctional Ras and Rap GTPase-activating proteins
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DOI：
10.1074/jbc.m512802200
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发表时间：
2006-04-14
影响因子：
4.8
通讯作者：
Cullen, PJ
中科院分区：
文献类型：
--
作者：
Kupzig, S;Deaconescu, D;Cullen, PJ
GAP1（IP4BP）是Ras gtpase激活蛋白（Ras GAPs） GAP1家族的成员，包括GAP1(m)、CAPRI和RASAL。GAP1（IP4BP）由中央Ras GAP结构域组成，由氨基末端C-2结构域和羧基末端pleckstrin同源/Bruton's酪氨酸激酶结构域包围，先前已被证明在Ras相关蛋白Rap上具有意想不到的GAP活性，除了预测的Ras GAP活性（Cullen， P. J., Hsuan， J. J., Truong， O., Letcher, a . J., Jackson， T. R., Dawson, a . P.和Irvine， R. F. (1995) Nature 376, 527 - 530）。在这里，我们已经证明GAP1IP4BP确实是一个有效的Ras/Rap GAP， Ras和Rap的K(m)s分别为213和42 μ m，估计K(cat)s分别为48和16 s（-1）。对于这种双重活性，Ras GAP结构域外的区域是必需的，因为分离的结构域（残基291 - 569）保留了明显的Ras GAP活性，但对Rap的活性非常低。有趣的是，RasGAP精氨酸指及其周围Ras结合重要残基的突变抑制了GAP1（IP4BP）的Ras和Rap GAP活性。尽管GAP1（IP4BP）作为Rap GAP的确切细节仍有待确定，但这些数据与Rap通过Ras GAP域中的Ras结合位点与GAP1（IP4BP）相关联是一致的。最后，我们已经确定这种双Ras/Rap GAP活性并不局限于GAP1（IP4BP）。虽然GAP1(m)似乎构成了特定的Ras GAP，但CAPRI和RASAL表现出双重活性。对于CAPRI，其Rap GAP活性是通过Ca2+诱导的与质膜的结合来调节的。
GAP1(IP4BP) is a member of the GAP1 family of Ras GTPase-activating proteins ( Ras GAPs) that includes GAP1(m), CAPRI, and RASAL. Composed of a central Ras GAP domain, surrounded by amino-terminal C-2 domains and a carboxyl-terminal pleckstrin homology/Bruton's tyrosine kinase domain, GAP1(IP4BP) has previously been shown to possess an unexpected GAP activity on the Ras-related protein Rap, besides the predicted Ras GAP activity (Cullen, P. J., Hsuan, J. J., Truong, O., Letcher, A. J., Jackson, T. R., Dawson, A. P., and Irvine, R. F. ( 1995) Nature 376, 527 - 530). Here we have shown that GAP1IP4BP is indeed an efficient Ras/Rap GAP, having K(m)s of 213 and 42 mu M and estimated k(cat)s of 48 and 16 s(-1) for Ras and Rap, respectively. For this dual activity, regions outside the Ras GAP domain are required, as the isolated domain ( residues 291 - 569) retains a pronounced Ras GAP activity yet has very low activity toward Rap. Interestingly, mutagenesis of the RasGAP arginine finger, and surrounding residues important in Ras binding, inhibit both Ras and Rap GAP activity of GAP1(IP4BP). Although the precise details by which GAP1(IP4BP) can function as a Rap GAP remain to be determined, these data are consistent with Rap associating with GAP1(IP4BP) through the Ras-binding site within the Ras GAP domain. Finally, we have established that such dual Ras/Rap GAP activity is not restricted to GAP1(IP4BP). Although GAP1(m) appears to constitute a specific Ras GAP, CAPRI and RASAL display dual activity. For CAPRI, its Rap GAP activity is modulated upon its Ca2+-induced association with the plasma membrane.