The role of backbone stability near Ala44 in the high reduction potential class of rubredoxins.
The role of backbone stability near Ala44 in the high reduction potential class of rubredoxins.
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Ala44 附近主链稳定性在高还原电位类红氧还蛋白中的作用。
DOI：
10.1002/prot.20806
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
Ichiye,Toshiko
中科院分区：
文献类型：
--
作者：
Tan,Ming-Liang;Kang,ChulHee;Ichiye,Toshiko
Rubredoxins可分为高还原电位和低还原电位两类，还原电位相差约50 mV。我们之前的工作表明，由于A44与V44侧链大小导致的极性主链的局部位移导致了这种还原电位差。然而，这项工作也表明，在低潜力的巴氏梭菌（Cp）红氧还蛋白中，V44→ A44突变导致更大的局部骨架灵活性，因为野生型（wt）中存在的V44侧链不再与相邻残基互锁以稳定随后的G45。由于Pyrococcus furiosus（Pf）和其他高潜力的红氧还蛋白一般都有一个P45，推测Cp红氧还蛋白的G45→ P45突变可能稳定V44→ A44突变。本文对野生型V44 G45、单突变型A44 G45和双突变型A44 P45 Cp以及野生型A44 P45 Pf红蛋白进行了晶体结构分析、能量最小化和分子动力学（MD）。CP的局部结构、动力学和静电性质逐渐接近WT Pf，顺序为WT Cp到单突变体到双突变体，因为如预期的那样，具有更大的序列相似性。双突变体A44P45Cp在残基44附近表现出增加的骨架稳定性，从而提高了骨架偶极子指向氧化还原位点的可能性，这有利于增加静电对还原电位的贡献。看来，残基44的静电势和溶剂对氧化还原的可及性都是同源rubredoxins的还原电位的决定因素。总的来说，这些结果表明，红氧还蛋白中的A44可能需要P45来保持骨架稳定，而V44可以容纳G45，因为缬氨酸侧链可以与其相邻的侧链互锁。Proteins 2006.© 2005 Wiley‐利斯公司
Rubredoxins may be separated into high and low reduction potential classes, with reduction potentials differing by ∼50 mV. Our previous work showed that a local shift in the polar backbone due to an A44versus V44side‐chain size causes this reduction potential difference. However, this work also indicated that in the low potentialClostridium pasteurianum(Cp) rubredoxin, a V44→ A44mutation causes larger local backbone flexibility, because the V44side‐chain present in the wild‐type (wt) is no longer present to interlock with neighboring residues to stabilize the subsequent G45. SincePyrococcus furiosus(Pf) and other high potential rubredoxins generally have a P45, it was presumed that a G45→ P45mutation might stabilize a V44→ A44mutation in Cp rubredoxin. Here crystal structure analysis, energy minimization, and molecular dynamics (MD) were performed for wt V44G45, single mutant A44G45and double mutant A44P45Cp, and for wt A44P45Pf rubredoxins. The local structural, dynamical, and electrostatic properties of Cp gradually approach wt Pf in the order wt Cp to single to double mutant because of greater sequence similarity, as expected. The double mutant A44P45Cp exhibits increased backbone stability near residue 44 and thus enhances the probability that the backbone dipoles point toward the redox site, which favors an increase in the electrostatic contribution to the reduction potential. It appears that the electrostatic potential of residue 44 and the solvent accessibility to the redox are both determinants for the reduction potentials of homologous rubredoxins. Overall, these results indicate that an A44in a rubredoxin may require a P45for backbone stability whereas a V44can accommodate a G45, since the valine side‐chain can interlock with its neighbors. Proteins 2006. © 2005 Wiley‐Liss, Inc.