Induced fit in guanidino kinases - comparison of substrate-free and transition state analog structures of arginine kinase
Induced fit in guanidino kinases - comparison of substrate-free and transition state analog structures of arginine kinase
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DOI：
10.1110/ps.0226303
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发表时间：
2003-01-01
期刊：
影响因子：
8
通讯作者：
Chapman, M
中科院分区：
文献类型：
--
作者：
Yousef, MS;Clark, SA;Chapman, M
精氨酸激酶(AK)是鸟嘌呤核苷酸激酶家族中的一员，在高能量需求和高能量需求的细胞中起着缓冲ATP浓度的重要作用。AK特异性催化三磷酸腺苷和精氨酸之间的可逆磷酸转移。我们测定了河蟹开放(无底物)形式的AK的晶体结构。最终的模型在2.35埃的温度下进行了精化，最终的R值为22.3%(无R值=23.7%)。将开放形式的结构与先前确定的闭合形式的过渡态模拟络合物的结构进行比较。经典的蛋白质结构会被认为是两个结构域，但动态结构域(Dynamic Dom)分析表明，两种结构之间的大部分差异可以被认为是四个刚性基团之间的运动。ATP结合在固定动态结构域的一簇带正电荷的残基附近。其他三个动态域通过相对于固定域的单独铰链旋转来关闭活动位置。几个对诱导运动至关重要的残基在磷酸化原激活酶家族中是保守的，包括肌酸激活酶。当与两种底物形成密切的相互作用时，在酶的不同部分诱导了实质性的构象变化。因此，尽管诱导FIT发生在许多磷酸转移酶中，但磷酸原激酶的构象变化似乎比先前的例子更复杂。
Arginine kinase (AK) is a member of the guanidino kinase family that plays an important role in buffering ATP concentration in cells with high and fluctuating energy demands. The AK specifically catalyzes the reversible phosphoryl transfer between ATP and arginine. We have determined the crystal structure of AK from the horseshoe crab (Limulus polyphemus) in its open (substrate-free) form. The final model has been refined at 2.35 Angstrom with a final R of 22.3% (R-free = 23.7%). The structure of the open form is compared to the previously determined structure of the transition state analog complex in the closed form. Classically, the protein would be considered two domain, but dynamic domain (DynDom) analysis shows that most of the differences between the two structures can be considered as the motion between four rigid groups of nonsequential residues. ATP binds near a cluster of positively charged residues of a fixed dynamic domain. The other three dynamic domains close the active site with separate hinge rotations relative to the fixed domain. Several residues of key importance for the induced motion are conserved within the phosphagen kinase family, including creatine kinase. Substantial conformational changes are induced in different parts of the enzyme as intimate interactions are formed with both substrates. Thus, although induced fit occurs in a number of phosphoryl transfer enzymes, the conformational changes in phosphagen kinases appear to be more complicated than in prior examples.