四氯合铂酸钾(K_2PtCl_4)与细胞色素c(Cyt·c)修饰体系的进一步研究

从K_2PtCl_4与Cyt·c反应产物中分离得四个组分,SDS-PAGE及元素分析测定结果表明,它们分别对应于Cyt·c寡聚体、三聚体、二聚体及单体。这揭示了K_2PtCl_4对Cyt·c存在多位点修饰,南非如Kostic报道的Met-65为其唯一修饰位点。通过K_2PtCl_4与羧甲基化Cyt·c修饰产物的分析研究,证实了另一标记位点His-33的存在。对Cyt·c二聚体衍生物的还原电位、紫外一可見及红外光谱研究表明,Cyt·c血红素周围的电子环境仍保持完整,但其二级结构有较大的扰动。

Further Studies on the Platinum-Modified Cytochrome c Complexes

The reaction mixture of Cyt·c and K_2PtCl_4 was separated by Sephadex G-75 to four components containing the oligmer,trimer, dimer and monomer respectively, as shown by SDS-PAGE molecular weight determination. This fact indicated that the Cyt·c might be polymerized with the platinum reagent through two or more sites rather than only Met-65 as reported by Kostic.This speculation was strongly supported by the selective block of His-33 and subsequent reaction results, as well as by the examination of the reactions of histidineand methionine with K_2PtCl_4 nuder the same condition as used for the native Cyt.c.The effect of the dimerization on the structure feature of the Cyt·c in direct complex was further examined by UVvisible spectroscopy and second derivative FT-IR technique.The results showed that the electronic enviroment of hame within the Cyt·c dimer remained intact, but there was significant pertubance on the secondary structure, especially the α-helix content of the Cyt·c of the dimer.