In the structural biology of bacterial substrate-binding proteins (SBPs), a growing number of comparisons between substrate-bound and substrate-free forms of metal atom-binding (cluster A-I) SBPs have revealed minimal structural differences between forms. These observations contrast with SBPs that bind substrates such as amino acids or nucleic acids and may undergo >60° rigid-body rotations. Substrate transfer in these SBPs is described by a Venus flytrap model, although this model may not apply to all SBPs. In this report, structures are presented of substrate-free (apo) and reconstituted substrate-bound (holo) YfeA, a polyspecific cluster A-I SBP from Yersinia pestis. It is demonstrated that an apo cluster A-I SBP can be purified by fractionation when co-expressed with its cognate transporter, adding an alternative strategy to the mutagenesis or biochemical treatment used to generate other apo cluster A-I SBPs. The apo YfeA structure contains 111 disordered protein atoms in a mobile helix located in the flexible carboxy-terminal lobe. Metal binding triggers a 15-fold reduction in the solvent-accessible surface area of the metal-binding site and reordering of the 111 protein atoms in the mobile helix. The flexible lobe undergoes a 13.6° rigid-body rotation that is driven by a spring-hammer metal-binding mechanism. This asymmetric rigid-body rotation may be unique to metal atom-binding SBPs (i.e. clusters A-I, A-II and D-IV).

中文翻译：

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apo 和锌重建的全息形式中的底物结合蛋白 YfeA 的结构。

在细菌底物结合蛋白 (SBP) 的结构生物学中，越来越多的底物结合形式和无底物形式的金属原子结合 (AI 簇) SBP 之间的比较揭示了形式之间的最小结构差异。这些观察结果与 SBP 形成对比，SBP 结合氨基酸或核酸等底物，并且可能经历 >60° 的刚体旋转。这些 SBP 中的底物转移由维纳斯捕蝇草模型描述，尽管该模型可能不适用于所有 SBP。在本报告中，介绍了无底物 (apo) 和重组底物结合 (holo) YfeA 的结构，YfeA 是来自鼠疫耶尔森氏菌的多特异性簇 AI SBP。结果表明，当apo簇AI SBP与其同源转运蛋白共表达时，可以通过分级纯化，为用于生成其他apo簇AI SBP的诱变或生化处理添加替代策略。apo YfeA 结构在位于柔性羧基末端叶中的移动螺旋中包含 111 个无序蛋白质原子。金属结合引发金属结合位点溶剂可及表面积减少 15 倍，并导致移动螺旋中 111 个蛋白质原子重新排序。柔性凸角经历 13.6° 刚体旋转，由弹簧锤金属绑定机构驱动。这种不对称刚体旋转可能是金属原子结合 SBP（即簇 AI、A-II 和 D-IV）所独有的。