BACKGROUND Polymyxin B resistance protein D (PmrD) plays a key role in the polymyxin B-resistance pathway, as it is the signaling protein that can act as a specific connecter between PmrA/PmrB and PhoP/PhoQ. We conducted structural analysis to characterize Escherichia coli (E. coli) PmrD, which exhibits different features compared with PmrD in other bacteria. RESULTS The X-ray crystal structure of E. coli PmrD was determined at a 2.00 Å resolution, revealing novel information such as the unambiguous secondary structures of the protein and the presence of a disulfide bond. Furthermore, various assays such as native gel electrophoresis, surface plasmon resonance (SPR), size-exclusion chromatography, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) measurements, were performed to elucidate the structural and functional role of the internal disulfide bond in E. coli PmrD. CONCLUSIONS The structural characteristics of E. coli PmrD were clearly identified via diverse techniques. The findings help explain the different protective mechanism of E. coli compared to other Gram-negative bacteria.

中文翻译：

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X射线晶体学和小角度X射线散射对大肠杆菌多粘菌素B抗性蛋白D的结构见解。

背景技术多粘菌素B抗性蛋白D（PmrD）在多粘菌素B抗性途径中起关键作用，因为它是可以充当PmrA / PmrB与PhoP / PhoQ之间的特异性连接子的信号传导蛋白。我们进行了结构分析，以鉴定大肠杆菌（E. coli）PmrD，与其他细菌中的PmrD相比，它表现出不同的特征。结果大肠杆菌PmrD的X射线晶体结构以2.00Å的分辨率测定，揭示了新颖的信息，如蛋白质的明确二级结构和二硫键的存在。此外，还进行了各种检测，例如天然凝胶电泳，表面等离子体共振（SPR），尺寸排阻色谱，动态光散射（DLS）和小角X射线散射（SAXS）测量，进行了研究以阐明大肠杆菌PmrD中内部二硫键的结构和功能作用。结论通过多种技术可以清楚地鉴定出大肠杆菌PmrD的结构特征。这些发现有助于解释与其他革兰氏阴性细菌相比，大肠杆菌的不同保护机制。