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Interdomain Conformational Changes Provide Allosteric Regulation en Route to Chorismate

机译:域间构象变化提供了构象调节从而实现了分支化

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摘要

Multifunctional proteins play a variety of roles in metabolism. Here, we examine the catalytic function of the combined 3-deoxy-d-arabino heptulosonate-7-phosphate synthase (DAH7PS) and chorismate mutase (CM) from Geobacillus sp. DAH7PS operates at the start of the biosynthetic pathway for aromatic metabolites, whereas CM operates in a dedicated branch of the pathway for the biosynthesis of amino acids tyrosine and phenylalanine. In line with sequence predictions, the two catalytic functions are located in distinct domains, and these two activities can be separated and retain functionality. For the full-length protein, prephenate, the product of the CM reaction, acts as an allosteric inhibitor for the DAH7PS. The crystal structure of the full-length protein with prephenate bound and the accompanying small angle x-ray scattering data reveal the molecular mechanism of the allostery. Prephenate binding results in the tighter association between the dimeric CM domains and the tetrameric DAH7PS, occluding the active site and therefore disrupting DAH7PS function. Acquisition of a physical gating mechanism to control catalytic function through gene fusion appears to be a general mechanism for providing allostery for this enzyme.
机译:多功能蛋白质在新陈代谢中起多种作用。在这里,我们检查了来自Geobacillus sp。的3-deoxy-d-arabino hepulosonate-7-phosphate synthase(DAH7PS)和chorismate mutase(CM)的催化功能。 DAH7PS在芳香族代谢物生物合成途径的开始起作用,而CM在氨基酸酪氨酸和苯丙氨酸的生物合成途径的专门分支中起作用。与序列预测一致,两个催化功能位于不同的域中,并且这两个活动可以分开并保留功能。对于全长蛋白质,CM反应产物prephenate充当DAH7PS的变构抑制剂。结合有苯甲酸酯的全长蛋白质的晶体结构以及伴随的小角度X射线散射数据揭示了变构的分子机理。苯甲酸酯的结合导致二聚体CM域与四聚体DAH7PS之间的紧密结合,从而遮挡了活性位点,从而破坏了DAH7PS的功能。通过基因融合获得物理门控机制以控制催化功能似乎是为该酶提供变构作用的一般机制。

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