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兔骨骼肌AMP脱氨酶金属中心的表征。双核锌位点的证据。

Characterization of the metallocenter of rabbit skeletal muscle AMP deaminase. Evidence for a dinuclear zinc site.

作者信息

Mangani Stefano, Benvenuti Manuela, Moir Arthur J G, Ranieri-Raggi Maria, Martini Daniela, Sabbatini Antonietta R M, Raggi Antonio

机构信息

Dipartimento di Chimica, Università di Siena, Via Aldo Moro, 53100-Siena, Italy; CERM, Università di Firenze, Via Luigi Sacconi 6, 50019 Firenze, Italy.

出版信息

Biochim Biophys Acta. 2007 Feb;1774(2):312-22. doi: 10.1016/j.bbapap.2006.12.005. Epub 2006 Dec 23.

Abstract

XAS of Zn-peptide binary and ternary complexes prepared using peptides mimicking the potential metal binding sites of rabbit skeletal muscle AMP deaminase (AMPD) strongly suggest that the region 48-61 of the enzyme contains a zinc binding site, whilst the region 360-372 of the enzyme is not able to form 1:1 complexes with zinc, in contrast with what has been suggested for the corresponding region of yeast AMPD. XAS performed on fresh preparations of rabbit skeletal muscle AMPD provides evidence for a dinuclear zinc site in the enzyme compatible with a (mu-aqua)(mu-carboxylato)dizinc(II) core with an average of two histidine residues at each metal site and a Zn-Zn distance of about 3.3 Angstrom. The data indicate that zinc is not required for HPRG/AMPD interaction, both zinc ions being bound to the catalytic subunit of the enzyme, one to the three conserved amino acid residues among those four assumed to be in contact with zinc in yeast AMPD, and the other at the N-terminal region, probably to His-52, Glu-53 and His-57. Tryptic digests of different enzyme preparations demonstrate the existence of two different protein conformations and of a zinc ion connecting the N-terminal and C-terminal regions of AMPD.

摘要

使用模拟兔骨骼肌AMP脱氨酶(AMPD)潜在金属结合位点的肽制备的锌-肽二元和三元配合物的X射线吸收光谱(XAS)强烈表明,该酶的48-61区域含有一个锌结合位点,而该酶的360-372区域不能与锌形成1:1配合物,这与酵母AMPD相应区域的情况相反。对兔骨骼肌AMPD新鲜制剂进行的XAS为该酶中的双核锌位点提供了证据,该位点与一个(μ-水)(μ-羧基)二锌(II)核心兼容,每个金属位点平均有两个组氨酸残基,锌-锌距离约为3.3埃。数据表明,锌对于HPRG/AMPD相互作用不是必需的,两个锌离子都与该酶的催化亚基结合,一个与酵母AMPD中假定与锌接触的四个保守氨基酸残基中的三个结合,另一个在N端区域,可能与His-52、Glu-53和His-57结合。不同酶制剂的胰蛋白酶消化证明存在两种不同的蛋白质构象以及一个连接AMPD N端和C端区域的锌离子。

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