Structural determinants of nitroxide motion in spin-labeled proteins: Solvent-exposed sites in helix B of T4 lysozyme
Structural determinants of nitroxide motion in spin-labeled proteins: Solvent-exposed sites in helix B of T4 lysozyme
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DOI：
10.1110/ps.073174008
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发表时间：
2008-02-01
期刊：
影响因子：
8
通讯作者：
Hubbell, Wayne L.
中科院分区：
文献类型：
--
作者：
Guo, Zhefeng;Cascio, Duilio;Hubbell, Wayne L.
定点自旋标记为探索蛋白质的结构和动力学提供了一种手段。为了解释经常出现的复杂EPR谱，有必要表征自旋标记侧链的旋转异构体以及它们与已知结构蛋白质中局部环境的相互作用。为此目的，已经确定了在B螺旋中的溶剂暴露的螺旋位点41和44处具有氮氧侧链（R1）的T4溶菌酶的晶体结构。这些网站是特别感兴趣的，相应的EPR光谱揭示了两个动态状态的R1，其中之一是相对固定的氮氧自由基与环境的相互作用。晶体结构以及最近邻突变对R1运动的影响表明41 R1与i + 4残基和44 R1与i + 1残基的螺旋内相互作用。这种相互作用似乎是特定的R1侧链的特定旋转异构体。
Site-directed spin labeling provides a means for exploring structure and dynamics in proteins. To interpret the complex EPR spectra that often arise, it is necessary to characterize the rotamers of the spin-labeled side chain and the interactions they make with the local environment in proteins of known structure. For this purpose, crystal structures have been determined for T4 lysozyme bearing a nitroxide side chain (R1) at the solvent-exposed helical sites 41 and 44 in the B helix. These sites are of particular interest in that the corresponding EPR spectra reveal two dynamic states of R1, one of which is relatively immobilized suggesting interactions of the nitroxide with the environment. The crystal structures together with the effect of mutagenesis of nearest neighbors on the motion of R1 suggest intrahelical interactions of 41R1 with the i + 4 residue and of 44R1 with the i + 1 residue. Such interactions appear to be specific to particular rotamers of the R1 side chain.