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首页> 外文期刊>Journal of Molecular Biology >Exploring the role of alanine in the structure of the Lac repressor tetramerization domain, a ferritin-like Alacoil.
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Exploring the role of alanine in the structure of the Lac repressor tetramerization domain, a ferritin-like Alacoil.

机译：探索丙氨酸在Lac阻遏物四聚化结构域（铁蛋白样Alacoil）的结构中的作用。

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摘要

We are interested in the determinants that specify the structure of antiparallel coiled coils. Antiparallel coiled coils often contain alanine as an important interfacial packing residue; structures containing alanine at certain well-defined positions in the heptad-repeating unit are referred to as Alacoils. Two types have been identified, containing alanine at either the g position of the heptad repeating unit (defined as the d position in the Richardson nomenclature), referred to as a rop-like Alacoil, or the e position (a position in the Richardson nomenclature), referred to as a ferritin-like Alacoil. The Lac repressor tetramerization domain forms an antiparallel four-chain coiled coil, which falls into the second class of Alacoils based on recent crystal structures. The role of alanine in such structures has not yet been explored experimentally. We test the importance of alanine at the e positions on the oligomeric state and stability of the isolated coiled-coil domain of Lac repressor by testing the effect of mutations at this position. We find that mutation to leucine is tolerated and its moderately stabilizing effect is most likely a consequence of plasticity of this motif. The effects on stability of the mutations to either serine or glutamine can be largely accounted for by helix propensity differences between these residues and alanine. The ability of the helices to adjust to such mutations, while maintaining the basic fold of this coiled coil, was further tested by making the same changes at the more highly exposed g position. Leucine at the g positions also causes an increase in stability, presumably by subtle rearrangement of the helices to allow partial desolvation of this side-chain.
机译：我们对确定反平行线圈的结构的决定因素感兴趣。反平行盘绕线圈通常含有丙氨酸作为重要的界面填料残渣。在七体重复单元中某些明确定义的位置上包含丙氨酸的结构称为Alacoils。已经鉴定出两种类型，在庚烷重复单元的g位置（在Richardson命名法中定义为d位置）（称为绳状Alacoil）或e位置（在Richardson命名法中的位置）包含丙氨酸），称为铁蛋白状Alacoil。 Lac阻遏物四聚结构域形成一个反平行的四链卷曲螺旋，根据最近的晶体结构，它属于第二类Alacoils。尚未通过实验探索丙氨酸在此类结构中的作用。我们通过测试在此位置突变的影响，测试了丙氨酸在寡聚状态的e位置上的重要性以及Lac阻遏物分离的卷曲螺旋结构域的稳定性。我们发现亮氨酸突变是可以忍受的，其适度稳定作用最有可能是该基序可塑性的结果。这些残基和丙氨酸之间螺旋倾向的差异很大程度上可以解释对丝氨酸或谷氨酰胺突变稳定性的影响。通过在暴露度更高的g位置进行相同的改变，进一步测试了螺旋调节此类突变的能力，同时保持了该卷曲螺旋的基本折叠。 g位置的亮氨酸也可能导致稳定性增加，可能是由于螺旋的细微重排使得该侧链部分去溶剂化所致。

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