Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA.
J Inorg Biochem. 2012 May;110:72-82. doi: 10.1016/j.jinorgbio.2012.02.002. Epub 2012 Feb 12.
Methanobactin (mb) is the first characterized example of a chalkophore, a class of copper-binding chromopeptides similar to iron-binding siderophores. Structural, redox, themodynamic, and spectral studies on chalkophores have focused almost exclusively on the mb from Methylosinus trichosporium OB3b (mb-OB3b). The structural characterization of a second mb from Methylocystis strain SB2 (mb-SB2) provides a means to examine the core structural features and metal binding properties of this group of chromopeptides. With the exception of the 5-membered rings (either oxazolone or imidazolone), enethiol groups, and the N-terminus oxo group, the structure of mb-SB2 differs markedly from mb-OB3b. In particular the amino acids commonly associated with metal coordination and redox activity found in mb-OB3b, Cys, Met, and Try, are replaced by Ala or are missing in mb-SB2. In this report the spectral and thermodynamic properties of mb-SB2 are presented and compared to mb-OB3b. The results demonstrate that the spectral and basic copper binding properties of both methanobactins are similar and the unique copper binding capacity of both methanobactins lies primarily in the pair of five-membered rings and associated enethiol groups. The remaining portions of the methanobactin appear to provide the scaffolding that brings together of the two ring systems to produce the tetrahedral binding site for copper binding.
甲烷菌素（mb）是第一个被描述的 chalkophore ，一类与铁结合的 siderophores 类似的铜结合色肽。 chalkophores 的结构、氧化还原、热力学和光谱研究几乎完全集中在来自 Methylosinus trichosporium OB3b 的 mb（mb-OB3b）上。来自 Methylocystis 菌株 SB2 的第二个 mb（mb-SB2）的结构表征为研究这群色肽的核心结构特征和金属结合特性提供了一种手段。除了 5 元环（oxazolone 或 imidazolone）、烯硫醇基团和 N-末端的氧基团外，mb-SB2 的结构与 mb-OB3b 明显不同。特别是与金属配位和氧化还原活性相关的常见氨基酸，如 Cys、Met 和 Try，在 mb-OB3b 中被 Ala 取代或缺失，而在 mb-SB2 中则不存在。本报告介绍了 mb-SB2 的光谱和热力学性质，并与 mb-OB3b 进行了比较。结果表明，两种甲烷菌素的光谱和基本铜结合性质相似，两种甲烷菌素的独特铜结合能力主要在于五元环对和相关的烯硫醇基团。甲烷菌素的其余部分似乎为两个环系统的结合提供了支架，从而产生了铜结合的四面体结合位点。
