Structure and metal-binding properties of PA4063, a novel player in periplasmic zinc trafficking by Pseudomonas aeruginosa.
Structure and metal-binding properties of PA4063, a novel player in periplasmic zinc trafficking by Pseudomonas aeruginosa.
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DOI：
10.1107/s2059798321009608
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发表时间：
2021-11-01
期刊：
影响因子：
--
通讯作者：
Ilari A
中科院分区：
文献类型：
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作者：
Fiorillo A;Battistoni A;Ammendola S;Secli V;Rinaldo S;Cutruzzolà F;Demitri N;Ilari A
介绍了 PA4063 的结构和锌结合特性，PA4063 是铜绿假单胞菌在缺锌条件下表达的周质蛋白之一。 PA4063 具有非典型的铁氧还蛋白样折叠。两个具有微摩尔亲和力的锌结合位点暴露在外，位于结构的同一面上。脱辅基蛋白中的两个富含组氨酸的环是无序的，有助于其中一个位点的锌配位。这些发现强烈表明 PA4063 在锌运输中的作用，可能充当金属伴侣或运输系统的调节剂。在恶劣环境中获取必需营养素的能力是病原体的一项关键技能。在缺锌条件下，铜绿假单胞菌表达一组金属稳态控制系统，与其他革兰氏阴性细菌相比，该系统很复杂，并且仅得到部分表征。本文描述了 PA4063 蛋白（PA4063-PA4066 操纵子的第一个成分）的结构和锌结合特性。 PA4063 在其他生物体中没有同源物，其特征是存在两个富含组氨酸的序列。 ITC 滴定检测到两个具有微摩尔亲和力的锌结合位点。在有锌和无锌的情况下进行的晶体学表征揭示了α/β-三明治结构，由于其大小和拓扑结构不同，因此可以归类为非典型铁氧还蛋白样折叠。位于 N 末端以及 β3 和 β4 之间的富含组氨酸的延伸段在 apo 结构中是无序的，但一些残基在锌的存在下变得结构化，有助于两个位点之一的协调。以相对较低的亲和力结合两个锌离子的能力、不存在催化空腔以及存在两个富含组氨酸的环，这些性质和结构特征表明 PA4063 可能发挥周质锌伴侣的作用，或作为浓度传感器，有助于优化病原体对缺锌的反应。
The structural and zinc-binding properties of PA4063, one of the periplasmic proteins expressed by Pseudomonas aeruginosa under zinc-deficient conditions, are presented. PA4063 has a noncanonical ferredoxin-like fold. Two zinc-binding sites with micromolar affinity are exposed and are located on the same face of the structure. Two histidine-rich loops, which are disordered in the apoprotein, contribute to zinc coordination in one of the sites. These findings strongly suggest a role for PA4063 in zinc trafficking, possibly acting as a metal chaperone or as a regulator of a transport system. The capability to obtain essential nutrients in hostile environments is a critical skill for pathogens. Under zinc-deficient conditions, Pseudomonas aeruginosa expresses a pool of metal homeostasis control systems that is complex compared with other Gram-negative bacteria and has only been partially characterized. Here, the structure and zinc-binding properties of the protein PA4063, the first component of the PA4063–PA4066 operon, are described. PA4063 has no homologs in other organisms and is characterized by the presence of two histidine-rich sequences. ITC titration detected two zinc-binding sites with micromolar affinity. Crystallographic characterization, performed both with and without zinc, revealed an α/β-sandwich structure that can be classified as a noncanonical ferredoxin-like fold since it differs in size and topology. The histidine-rich stretches located at the N-terminus and between β3 and β4 are disordered in the apo structure, but a few residues become structured in the presence of zinc, contributing to coordination in one of the two sites. The ability to bind two zinc ions at relatively low affinity, the absence of catalytic cavities and the presence of two histidine-rich loops are properties and structural features which suggest that PA4063 might play a role as a periplasmic zinc chaperone or as a concentration sensor useful for optimizing the response of the pathogen to zinc deficiency.