Banci Lucia, Bertini Ivano, Ciofi-Baffoni Simone, Finney Lydia A, Outten Caryn E, O'Halloran Thomas V
Magnetic Resonance Center CERM and Department of Chemistry, University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Italy.
J Mol Biol. 2002 Nov 8;323(5):883-97. doi: 10.1016/s0022-2836(02)01007-0.
Zinc, a metal ion that functions in a wide variety of catalytic and structural sites in metalloproteins, is shown here to adopt a novel coordination environment in the Escherichia coli transport protein ZntA. The ZntA protein is a P-type ATPase that pumps zinc out of the cytoplasm and into the periplasm. It is physiologically selective for Zn(II) and functions with metalloregulatory proteins in the cell to keep the zinc quota within strict limits. Yet, the N-terminal cytoplasmic domain contains a region that is highly homologous to the yeast Cu(I) metallochaperone Atx1. To investigate how the structure of this region may influence its function, this fragment, containing residues 46-118, has been cloned out of the gene and overexpressed. We report here the solution structure of this fragment as determined by NMR. Both the apo and Zn(II)-ZntA(46-118) structures have been determined. It contains a previously unknown protein coordination site for zinc that includes two cysteine residues, Cys59 and Cys62, and a carboxylate residue, Asp58. The solvent accessibility of this site is also remarkably high, a feature that increasingly appears to be a characteristic of domains of heavy metal ion transport proteins. The participation of Asp58 in this ZntA metal ion binding site may play an important role in modulating the relative affinities and metal exchange rates for Zn(II)/Pb(II)/Cd(II) as compared with other P-type ATPases, which are selective for Cu(I) or Ag(I).
锌是一种金属离子，在金属蛋白的多种催化和结构位点发挥作用，本文显示其在大肠杆菌转运蛋白ZntA中采用了一种新型配位环境。ZntA蛋白是一种P型ATP酶，可将锌从细胞质泵出并转运至周质。它在生理上对Zn(II)具有选择性，并与细胞中的金属调节蛋白共同作用，将锌的含量控制在严格范围内。然而，其N端细胞质结构域包含一个与酵母Cu(I)金属伴侣蛋白Atx1高度同源的区域。为了研究该区域的结构如何影响其功能，已从基因中克隆出包含46 - 118位残基的片段并进行了过表达。我们在此报告通过核磁共振确定的该片段的溶液结构。已确定了脱辅基和Zn(II)-ZntA(46 - 118)的结构。它包含一个以前未知的锌蛋白配位位点，其中包括两个半胱氨酸残基Cys59和Cys62以及一个羧酸盐残基Asp58。该位点的溶剂可及性也非常高，这一特征越来越多地似乎是重金属离子转运蛋白结构域的一个特点。与其他对Cu(I)或Ag(I)具有选择性的P型ATP酶相比，Asp58参与该ZntA金属离子结合位点可能在调节Zn(II)/Pb(II)/Cd(II)的相对亲和力和金属交换速率方面发挥重要作用。
