Hannibal Luciana, Bunge Scott D, van Eldik Rudi, Jacobsen Donald W, Kratky Christoph, Gruber Karl, Brasch Nicola E
Department of Chemistry and School of Biomedical Sciences, Kent State University, Kent, Ohio 44242, USA.
Inorg Chem. 2007 Apr 30;46(9):3613-8. doi: 10.1021/ic070022n. Epub 2007 Apr 4.
The X-ray structures of imidazolylcobalamin (ImCbl) and histidinylcobalamin (HisCbl) are reported. These structures are of interest given that the recent structures of human and bovine transcobalamin prepared in their holo forms from aquacobalamin show a histidine residue of the metalloprotein bound at the beta-axial site of the cobalamin (Wuerges, J. et al. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 4386-4391). The beta-axial Co-N bond distances for ImCbl and HisCbl are 1.94(1) and 1.951(7) A, respectively. The alpha-axial Co-N bond distances to the 5,6-dimethylbenzimidazole are 2.01(1) and 1.979(8) A for ImCbl and HisCbl, respectively, and are typical for cobalamins with weak sigma-donor ligands at the beta-axial site. The corrin fold angles of 11.8(3) degrees (ImCbl) and 12.0(3) degrees (HisCbl) are smaller than those typically observed for cobalamins.
报道了咪唑钴胺素（ImCbl）和组氨酸钴胺素（HisCbl）的X射线结构。鉴于最近从水钴胺素制备的全态人转钴胺素和牛转钴胺素的结构显示金属蛋白的一个组氨酸残基结合在钴胺素的β-轴向位点（Wuerges，J.等人，《美国国家科学院院刊》，2006年，103卷，4386 - 4391页），这些结构备受关注。ImCbl和HisCbl的β-轴向Co - N键距离分别为1.94(1) Å和1.951(7) Å。对于ImCbl和HisCbl，与5,6 - 二甲基苯并咪唑的α-轴向Co - N键距离分别为2.01(1) Å和1.979(8) Å，这对于在β-轴向位点具有弱σ-供体配体的钴胺素来说是典型的。ImCbl的11.8(3)度和HisCbl的12.0(3)度的咕啉折叠角小于钴胺素通常观察到的角度。
