Electrostatic interactions in the assembly of Escherichia coli aspartate transcarbamylase.
Electrostatic interactions in the assembly of Escherichia coli aspartate transcarbamylase.
复制标题
大肠杆菌天冬氨酸转氨甲酰酶组装中的静电相互作用。
DOI：
10.1002/prot.340050108
复制
发表时间：
1989
期刊：
影响因子：
2.9
通讯作者：
Allewell,NM
中科院分区：
文献类型：
--
作者：
Glackin,MP;McCarthy,MP;Mallikarachchi,D;Matthew,JB;Allewell,NM
虽然可电离基团在大肠杆菌天冬氨酸转氨甲酰酶的组装、催化和调节机制中起着重要作用，但这些基团尚未被详细表征。我们报告的应用静态可达性修改Tanford柯克伍德理论模型与组装的链，亚基，和全酶的静电效应。除R1-R6外，所有链间界面在pH 8时都通过静电相互作用稳定了−2至−4 kcal−m− 1。亚基间接触（C1-C2和R1-R6）的稳定自由能的静电分量的pH依赖性与亚基间接触（C1-C4、C1-R1和C1-R4）的静电分量的pH依赖性在性质上是不同的。这种差异可以允许跨子单元接口的信息传输被选择性地调节。已经确定了由于蛋白质-蛋白质相互作用而导致计算的pK或电荷变化的组，并且结果与关于其功能的可用信息相关。c链的240 s环和r链的Zn（II）离子附近的区域都含有可电离基团的簇，其计算的pK值在组装时变化相对较大。这些pK的变化反过来又延伸到远离界面的蛋白质区域。可电离基团的网络参与结合位点之间的信息传输的可能性建议。
Although ionizable groups are known to play important roles in the assembly, catalytic, and regulatory mechanisms ofEscherichia coliaspartate transcarbamylase, these groups have not been characterized in detail. We report the application of static accessibility modified Tanford‐Kirkwood theory to model electrostatic effects associated with the assembly of pair of chains, subunits, and the holoenzyme. All of the interchain interfaces except R1–R6 are stabilized by electrostatic interactions by −2 to −4 kcal−m−1at pH 8. The pH dependence of the electrostatic component of the free energy of stabilization ofintrasubunitcontacts (C1–C2 and R1–R6) is qualitatively different from that ofintersubunitcontacts (C1–C4, C1–R1, and C1–R4). This difference may allow the transmission of information across subunit interfaces to be selectively regulated. Groups whose calculated pK or charge changes as a result of protein‐protein interactions have been identified and the results correlated with available information about their function. Both the 240s loop of the c chain and the region near the Zn(II) ion of the r chain contain clusters of ionizable groups whose calculated pK values change by relatively large amounts upon assembly. These pK changes in turn extend to regions of the protein remote from the interface. The possibility that networks of ionizable groups are involved in transmitting information between binding sites is suggested.