K_2PtCl_4与细胞色素C修饰体系研究

马心细胞色素C(以下简写为Cyt·C)与K_2PtCl_4的反应混合物在Sephadex G-75上分出4个组分,对应于Cyt·C寡聚体、三聚体、二聚体及单体,此结果与SDS聚丙烯酰胺凝胶电泳(以下简写为SDS-PAGE)测定的各组分的分子量相一致,这揭示了K_2PtCl_4与Cyt·C存在多位点修饰,而非如Kostic报道的Met-65为其唯一修饰位点,此结论通过分析K_2PtCl_4与His-33羧甲基化的Cyt·C修饰反应产物所证实,同时也和同样条件下游离His,Met与K_2PtCl_4的配位作用相吻合,对Cyt·C二聚体衍生物的还原电位、紫外-可见光谱以及二阶导数傅利叶变换红外光谱研究表明,血红素周围的电子环境仍然保持完整,但其二级结构有较大的扰动.

Studies on the Platinum-Modified Cytochrome C Complexes

The reaction mixture of cytochrome c and potassium platinochloride (K_2PtCl_4) was separated by Sephadex G-75 which gave four components contain the oligmer, trimer, dimer and monomer respectively, as shown by SDS-PAGE molecular weight determination. This fact indicated that the cytochrome c might be polymerized with the platinum reagent through two or more sites rather than only Met-65 reported by Kostic. This speculation was strongly supported by the selective block of His-33 and subsequent reaction result, as well as by the examination of the reactions of His and Met with K_2PtCl_4 under the same condition as used for the native cytochrome c. The effect of the dimerization on the structure feature of the cytochrome c in the dimer complex was further examined by UV-visible spectroscopy and the second derivative FT-IR technique, which suggested that the heme electronic environment of the dimer remained intact, but there was significant pertubation on the secondary structure, especially the a-helix content of the cytochrome c of the dimer.