Mutual Recognition and Electron Transfer of Electron Carriers: Cytochrome and Ferredoxin Systems

点击翻译按钮获取中文摘要

The cytochrome <C_1> subcomplex of beef heart mitochondria was reacted with 3 molar equivalents of pCMB to modify 3 SH-groups. The two subunits (heme-subunit and hinge protein) were not separated on gel filtration, but by electrophoresis after this treatment, leading to the appearance of autoxidizability of <C_1> heme subunit. This indicates that the hinge protein is indispensable not only for complex formation between <C_1> and c, but also for obstructing the <C_1> heme subunit from autoxidation. The heme subunit seems to polymerize if the hinge protein is not associated.Some mutated genes of cytochrome <C_1> were introduced into yeast cells to see how they affect the growth of yeast, respiratory ability, spectral characteristics, assembly into mitochondrial inner membrane, and gene expression. The deletion of 17 amino acids from the carboxyl-terminal region of <C_1> did not affect at all these characteristics, but when 70 amino acids from the carboxyl-terminal region were deleted, the protein modified lost the ability to be integrated into complex III of respiratory chain, and growth as well as respiration. This was partly predicted when the structure of beef cytochrome <C_1> was established. The work on this line is very promising to elucidate structure-function relationship of not only cytochrome <C_1> , but other membranous proteins. Other works done during this term are as follows: Identification of the heme iron ligands, crystallizations of <C_1> and ferredoxin <NADP^+> reductase, characterization of SH-groups in this enzyme, and iron-sulfur cluster formation.