Crystal structure of a periplasmic solute binding protein in metal-free, intermediate and metal-bound states from Candidatus Liberibacter asiaticus
Crystal structure of a periplasmic solute binding protein in metal-free, intermediate and metal-bound states from Candidatus Liberibacter asiaticus
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DOI：
10.1016/j.jsb.2015.01.012
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发表时间：
2015-03-01
影响因子：
3
通讯作者：
Sharma, Ashwani Kumar
中科院分区：
文献类型：
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作者：
Sharma, Nidhi;Selvakumar, Purushotham;Sharma, Ashwani Kumar
Znu 系统是 ABC 转运蛋白家族的成员，对于亚洲自由杆菌 (CLA) 的生存和发病机制至关重要。已在 CLA 中鉴定出该系统的两个同源物。在这里，我们报道了 CLA 中 Znu 系统两个基因簇中第二个的周质溶质结合蛋白 (CLas-ZnuA2) 在无金属、中间和金属结合状态下的高分辨率晶体结构。 CLas-ZnuA2 与 A-I 簇家族的 Mn/Fe 特异性溶质结合蛋白 (SBP) 显示出最大的序列同一性。 CLas-ZnuA2 的整体折叠与相关的 A-I 家族 SBP 簇相似。序列和结构分析揭示了CLas-ZnuA2的独特特征。 CLas-ZnA2 结构在三种状态下的比较表明，金属结合残基之一（His39）以无金属形式从金属结合位点翻转时，大位移以及侧链方向的变化促进了金属结合和释放。在金属结合的中间状态下捕获的晶体结构揭示了金属结合期间承载 His39 的环的构象和相互作用的变化。正如 PsaA 报道的那样，在金属结合过程中，C 结构域的刚体运动以及其 C 末端接头螺旋的部分展开，在 CLas-ZnuA2 中没有观察到。目前的结果表明，尽管与 Mn/Fe 特异性 SBP 显示出最大的序列同一性，但 CLas-ZnuA2 的机械相似性似乎更接近簇 A-I 家族的 Zn 特异性 SBP。 (C) 2015 Elsevier Inc. 保留所有权利。
The Znu system, a member of ABC transporter family, is critical for survival and pathogenesis of Candidatus Liberibacter asiaticus (CLA). Two homologues of this system have been identified in CLA. Here, we report high resolution crystal structure of a periplasmic solute binding protein from second of the two gene clusters of Znu system in CLA (CLas-ZnuA2) in metal-free, intermediate and metal-bound states. CLas-ZnuA2 showed maximum sequence identity to the Mn/Fe-specific solute binding proteins (SBPs) of cluster A-I family. The overall fold of CLas-ZnuA2 is similar to the related cluster A-I family SBPs. The sequence and structure analysis revealed the unique features of CLas-ZnuA2. The comparison of CLas-ZnuA2 structure in three states showed that metal binding and release is facilitated by a large displacement along with a change in orientation of the side chain for one of the metal binding residue (His39) flipped away from metal binding site in metal-free form. The crystal structure captured in intermediate state of metal binding revealed the changes in conformation and interaction of the loop hosting His39 during the metal binding. A rigid body movement of C-domain along with partial unfolding of linker helix at its C-terminal during metal binding, as reported for PsaA, was not observed in CLas-ZnuA2. The present results suggest that despite showing maximum sequence identity to the Mn/Fe-specific SBPs, the mechanistic resemblance of CLas-ZnuA2 seems to be closer to Zn-specific SBPs of cluster A-I family. (C) 2015 Elsevier Inc. All rights reserved.