Kanteev Margarita, Adir Noam
Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel.
Acta Crystallogr Sect F Struct Biol Cryst Commun. 2013 Mar 1;69(Pt 3):237-42. doi: 10.1107/S174430911300153X. Epub 2013 Feb 22.
The cyanobacterium Synechocystis sp. PCC 6803 imports Mn2+ ions via MntCAB, an ABC transport system that is expressed at submicromolar Mn2+ concentrations. The structures of the wild type (WT) and a site-directed mutant of the MntC solute-binding protein have been determined at 2.7 and 3.5 Å resolution, respectively. The WT structure is significantly improved over the previously determined structure (PDB entry 1xvl), showing improved Mn2+ binding site parameters, disulfide bonds in all three monomers and ions bound to the protein surface, revealing the role of Zn2+ ions in the crystallization liquor. The structure of MntC reveals that the active site is surrounded by neutral-to-positive electrostatic potential and is dominated by a network of polar interactions centred around Arg116. The mutation of this residue to alanine was shown to destabilize loops in the entrance to the metal-ion binding site and suggests a possible role in MntC function.
集胞藻6803通过MntCAB摄取Mn2+离子，MntCAB是一种ABC转运系统，在亚微摩尔浓度的Mn2+条件下表达。已分别在2.7 Å和3.5 Å分辨率下测定了MntC溶质结合蛋白的野生型（WT）和定点突变体的结构。与之前测定的结构（PDB条目1xvl）相比，WT结构有显著改善，显示出改善的Mn2+结合位点参数、所有三个单体中的二硫键以及与蛋白质表面结合的离子，揭示了结晶液中Zn2+离子的作用。MntC的结构表明，活性位点被中性到正的静电势包围，并由以Arg116为中心的极性相互作用网络主导。该残基突变为丙氨酸会使金属离子结合位点入口处的环不稳定，并暗示其在MntC功能中可能发挥的作用。
