Journal of Inorganic Biochemistry ( IF 3.9 ) Pub Date : 2020-11-04 , DOI: 10.1016/j.jinorgbio.2020.111304 Denise Bellotti 1 , Angelica Sinigaglia 2 , Remo Guerrini 2 , Erika Marzola 2 , Magdalena Rowińska-Żyrek 3 , Maurizio Remelli 2
Helicobacter pylori is a gram-negative bacterium with gastric localization that can cause many gastrointestinal disorders. Its survival in the host environment strictly requires an efficient regulation of its metal homeostasis, in particular of Ni(II) ions, crucial for the synthesis of some essential enzymes. Hpn is a protein of 60 amino acids, 47% of which are histidines, expressed by H. pylori and avid for nickel, characterized by the presence of an ATCUN (Amino Terminal Cu(II)- and Ni(II)-binding) motif and by two further histidine residues which can act as additional metal anchoring sites. We decided to deepen the following aspects: (i) understanding the role of each histidine in the coordination of metal ions; (ii) comparing the binding affinities for Cu(II), Ni(II) and Zn(II) ions, which are potentially competing metals in vivo; (iii) understanding the Hpn ability of forming ternary and poly-nuclear complexes. For these purposes, we synthesized the Hpn N-terminal “wild-type” sequence (MAHHEEQHG-Am) and the following peptide analogues: MAAHEEQHG-Am, MAHAEEQHG-Am, MAHHEEQAG-Am and MAHAEEQAG-Am. Our results highlight that the histidines in position 4 and 8 lead to the formation of Cu(II) binuclear complexes. The ATCUN motif is by far the most efficient binding site for Cu(II) and Ni(II), while macrochelate Zn(II) complexes are formed thanks to the presence of several suitable anchoring sites (His and Glu). The metal binding affinities follow the order Zn(II) < Ni(II) < < Cu(II). In solutions containing equimolar amount of wild-type ligand, Cu(II) and Ni(II), the major species above pH 5.5 are hetero-binuclear complexes.
中文翻译:
幽门螺杆菌 Hpn 蛋白的 N 端结构域:多个组氨酸残基的作用
幽门螺杆菌是一种革兰氏阴性菌,定位于胃部,可引起许多胃肠道疾病。它在宿主环境中的生存严格要求有效调节其金属稳态,尤其是 Ni(II) 离子,这对于合成一些必需酶至关重要。Hpn 是一种由 60 个氨基酸组成的蛋白质,其中 47% 是组氨酸,由幽门螺杆菌表达并热衷于镍,其特征在于存在 ATCUN(氨基末端 Cu(II)-和 Ni(II)-结合)基序和另外两个组氨酸残基,可作为额外的金属锚定位点。我们决定从以下几个方面进行深入:(i)了解每个组氨酸在金属离子配位中的作用;(ii) 比较 Cu(II)、Ni(II) 和 Zn(II) 离子的结合亲和力,它们是体内潜在的竞争金属;(iii) 了解 Hpn 形成三元和多核配合物的能力。为了这些目的,我们合成了 Hpn N 端“野生型”序列 (MAHHEEQHG-Am) 和以下肽类似物:MAAHEEQHG-Am、MAHAEEQHG-Am、MAHHEEQAG-Am 和 MAHAEEQAG-Am。我们的结果强调,位置 4 和 8 的组氨酸导致形成 Cu(II) 双核复合物。ATCUN 基序是迄今为止最有效的 Cu(II) 和 Ni(II) 结合位点,而由于存在几个合适的锚定位点(His 和 Glu),形成了大螯合 Zn(II) 复合物。金属结合亲和力的顺序为 Zn(II) < Ni(II) < < Cu(II)。在含有等摩尔量的野生型配体、Cu(II) 和 Ni(II) 的溶液中,pH 5.5 以上的主要物质是异双核复合物。