Sun Y, Ramirez J, Woski S A, Vincent J B
Department of Chemistry and Coalition for Biomolecular Products, The University of Alabama, Tuscaloosa 35487-0336, USA.
J Biol Inorg Chem. 2000 Feb;5(1):129-36. doi: 10.1007/s007750050016.
A recent model for the role of chromium in insulin signaling requires that the oligopeptide low-molecular-weight chromium-binding substance (LMWCr) tightly bind four chromic ions before the oligopeptide obtains a conformation required for binding to the tyrosine kinase active site of the insulin receptor. To test this model, the chromium-binding constant of LMWCr was determined, and the ability of LMWCr to remove chromium from Cr2-transferrin and the nutritional supplement chromium picolinate, Cr(pic)3, was examined. These results are consistent with the model of the mode of action of LMWCr; a Hill study indicates the four chromic ions bind to apoLMWCr in a highly cooperative fashion (n =3.47) with a binding constant of 1.54x 10(21). Chromium is readily transferred from transferrin to apoLMWCr at near neutral pH. The results also suggest that reduction of the chromic center of Cr(pic)3 may be required for the supplement to release chromium; thus, release of chromium is related to a mechanism by which Cr(pic)3 may generate hydroxyl radicals in cells.
最近提出的一个关于铬在胰岛素信号传导中作用的模型认为，寡肽低分子量铬结合物质（LMWCr）在获得与胰岛素受体酪氨酸激酶活性位点结合所需的构象之前，必须紧密结合四个铬离子。为了验证该模型，测定了LMWCr的铬结合常数，并研究了LMWCr从Cr2-转铁蛋白和营养补充剂吡啶甲酸铬（Cr(pic)3）中去除铬的能力。这些结果与LMWCr的作用模式模型一致；一项希尔研究表明，四个铬离子以高度协同的方式（n = 3.47）与脱辅基LMWCr结合，结合常数为1.54×10(21)。在接近中性pH值时，铬很容易从转铁蛋白转移到脱辅基LMWCr。结果还表明，补充剂释放铬可能需要还原Cr(pic)3的铬中心；因此，铬的释放与Cr(pic)3在细胞中产生羟基自由基的机制有关。
