Department of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India.
FEBS Open Bio. 2012 Jul 27;2:173-7. doi: 10.1016/j.fob.2012.07.008. Print 2012.
GTPases are important regulatory proteins that hydrolyze GTP to GDP. A novel GTP-hydrolysis mechanism is employed by MnmE, YqeH and FeoB, where a potassium ion plays a role analogous to the Arginine finger of the Ras-RasGAP system, to accelerate otherwise slow GTP hydrolysis rates. In these proteins, two conserved asparagines and a 'K-loop' present in switch-I, were suggested as attributes of GTPases employing a K(+)-mediated mechanism. Based on their conservation, a similar mechanism was suggested for TEES family GTPases. Recently, in Dynamin, Fzo1 and RbgA, which also conserve these attributes, a similar mechanism was shown to be operative. Here, we probe K(+)-activated GTP hydrolysis in TEES (TrmE-Era-EngA-YihA-Septin) GTPases - Era, EngB and the two contiguous G-domains, GD1 and GD2 of YphC (EngA homologue) - and also in HflX, another GTPase that also conserves the same attributes. While GD1-YphC and Era exhibit a K(+)-mediated activation of GTP hydrolysis, surprisingly GD2-YphC, EngB and HflX do not. Therefore, the attributes identified thus far, do not necessarily predict a K(+)-mechanism in GTPases and hence warrant extensive structural investigations.
GTPases 是一种重要的调节蛋白，能够将 GTP 水解为 GDP。MnmE、YqeH 和 FeoB 采用了一种新颖的 GTP 水解机制，其中一个钾离子起到类似于 Ras-RasGAP 系统精氨酸指的作用，从而加速原本缓慢的 GTP 水解速率。在这些蛋白质中，两个保守的天冬酰胺和位于开关-I 中的“K 环”被认为是采用 K(+)-介导机制的 GTPases 的特征。基于其保守性，类似的机制也被提出用于 TEES 家族 GTPases。最近，在 Dynamin、Fzo1 和 RbgA 中，也保守这些属性，表明存在类似的机制。在这里，我们研究了 TEES（TrmE-Era-EngA-YihA-Septin）GTPases——Era、EngB 和 YphC（EngA 同源物）的两个连续 G 结构域 GD1 和 GD2——以及另一个保守相同属性的 GTPase HflX 中的 K(+)-激活的 GTP 水解。虽然 GD1-YphC 和 Era 表现出 K(+)-介导的 GTP 水解激活，但令人惊讶的是，GD2-YphC、EngB 和 HflX 则没有。因此，迄今为止确定的特征不一定能预测 GTPases 中的 K(+)-机制，因此需要进行广泛的结构研究。
