Analysis of GTPases carrying hydrophobic amino acid substitutions in lieu of the catalytic glutamine: Implications for GTP hydrolysis
Analysis of GTPases carrying hydrophobic amino acid substitutions in lieu of the catalytic glutamine: Implications for GTP hydrolysis
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DOI：
10.1002/prot.20413
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发表时间：
2005-05-01
影响因子：
2.9
通讯作者：
Prakash, B
中科院分区：
文献类型：
--
作者：
Mishra, R;Gara, SK;Prakash, B
Ras超家族GTP结合蛋白调节细胞中的重要信号事件。Ras通常作为原型，有效地水解GTP及其调节剂GAP。在大多数GTP结合蛋白中，保守的谷氨酰胺在GTP水解中起着至关重要的作用。Ras中的谷氨酰胺突变具有致癌作用，因为它破坏了GTP水解。这里介绍的分析是GTP结合蛋白，这是一个矛盾的致癌Ras，因为他们有催化谷氨酰胺（Gln（猫））取代的疏水氨基酸，但可以有效地水解GTP。我们将这些蛋白质称为HAS-GTP酶。HAS-GTP酶的氨基酸序列的分析揭示了在GTP结合口袋周围插入的突出存在。同源建模研究表明，一个有趣的手段，实现催化，尽管激烈的疏水取代取代的关键Gln（猫）的Ras样GTP酶。取代的疏水残基采用“收缩构象”，其中它远离GTP定位，因为它在催化中的作用将是非生产性的。通过与其附近的疏水性残基的相互作用，这种构象进一步稳定。这些相互作用的残基在所有HAS-GTP酶中是高度保守和疏水的，并且对应于Ras的残基Asp 92和Tyr 96。开关II的“收缩构象”的实验支持来自Ylqf和hGBP 1的晶体结构。这种构象使我们能够假设，与经典的GTP酶不同，催化残基可以由开关II以外的区域提供（即，插入或相邻结构域）。(c)2005 Wiley-Liss，Inc.
Ras superfamily GTP-binding proteins regulate important signaling events in the cell. Ras, which often serves as a prototype, efficiently hydrolyzes GTP in conjunction with its regulator GAP. A conserved glutamine plays a vital role in GTP hydrolysis in most GTP-binding proteins. Mutating this glutamine in Ras has oncogenic effects, since it disrupts GTP hydrolysis. The analysis presented here is of GTP-binding proteins that are a paradox to oncogenic Ras, since they have the catalytic glutamine (Gln(cat)) substituted by a hydrophobic amino acid, yet can hydrolyze GTP efficiently. We term these proteins HAS-GTPases. Analysis of the amino acid sequences of HAS-GTPases reveals prominent presence of insertions around the GTP-binding pocket. Homology modeling studies suggest an interesting means to achieve catalysis despite the drastic hydrophobic substitution replacing the key Gln(cat) of Ras-like GTPases. The substituted hydrophobic residue adopts a "retracted conformation," where it is positioned away from the GTP, as its role in catalysis would be unproductive. This conformation is further stabilized by interactions with hydrophobic residues in its vicinity. These interacting residues are strongly conserved and hydrophobic in all HAS-GTPases, and correspond to residues Asp92 and Tyr96 of Ras. An experimental support for the "retracted conformation" of Switch II arises from the crystal structures of Ylqf and hGBP1. This conformation allows us to hypothesize that, unlike in classical GTPases, catalytic residues could be supplied by regions other than the Switch II (i.e., either the insertions or a neighboring domain). (c) 2005 Wiley-Liss, Inc.