Banci Lucia, Bertini Ivano, Calderone Vito, Della-Malva Nunzia, Felli Isabella C, Neri Sara, Pavelkova Anna, Rosato Antonio
Magnetic Resonance Center (CERM), University of Florence, Sesto Fiorentino, Italy.
Biochem J. 2009 Jul 29;422(1):37-42. doi: 10.1042/BJ20090422.
The homoeostasis of metal ions in cells is the result of the contribution of several cellular pathways that involve transient, often weak, protein-protein interactions. Metal transfer typically implies the formation of adducts where the metal itself acts as a bridge between proteins, by co-ordinating residues of both interacting partners. In the present study we address the interaction between the human copper(I)-chaperone HAH1 (human ATX1 homologue) and a metal-binding domain in one of its partners, namely the P-type copper-transporting ATPase, ATP7A (ATPase, Cu+ transporting, alpha polypeptide). The adduct was structurally characterized in solution, in the presence of copper(I), and through X-ray crystallography, upon replacing copper(I) with cadmium(II). Further insight was obtained through molecular modelling techniques and site-directed mutagenesis. It was found that the interaction involves a relatively small interface (less than 1000 A(2), 1 A=0.1 nm) with a low fraction of non-polar atoms. These observations provide a possible explanation for the low affinity of the two apoproteins. It appears that electrostatics is important in selecting which domain of the ATPase is able to form detectable amounts of the metal-mediated adduct with HAH1.
细胞中金属离子的稳态是多种细胞途径共同作用的结果，这些途径涉及短暂的、通常较弱的蛋白质 - 蛋白质相互作用。金属转移通常意味着形成加合物，其中金属本身通过协调两个相互作用伙伴的残基，在蛋白质之间起到桥梁作用。在本研究中，我们研究了人类铜（I）伴侣蛋白HAH1（人类ATX1同源物）与其一个伙伴中的金属结合结构域之间的相互作用，该伙伴即P型铜转运ATP酶ATP7A（ATP酶，铜离子转运，α多肽）。在有铜（I）存在的情况下，通过溶液结构表征该加合物，并在将铜（I）替换为镉（II）后通过X射线晶体学进行表征。通过分子建模技术和定点诱变获得了进一步的见解。发现这种相互作用涉及一个相对较小的界面（小于1000 Ų，1 Å = 0.1 nm），非极性原子比例较低。这些观察结果为两种脱辅基蛋白的低亲和力提供了一种可能的解释。似乎静电作用在选择ATP酶的哪个结构域能够与HAH1形成可检测量的金属介导加合物方面很重要。
