A Function of the Hinge Protein c1-c
Treatment of the cytochrome C 1 subcomplex consisting of the heme subunit and the hinge protein with pCMB1 under appropriate conditions dissociated the two subunits on PAGE under non-denaturing conditions, but did not on gel filtration. The preparation bound three mol Hg,one on the hinge protein and two on the heme subunit. The pCMB-treated subcomplex had a slight autoxidizability which was repressed to the level of the native subcomplex upon treatment with 2-mercaptoethanol. Concomitantly, the subunits were apparently reversed to the native form not dissociable on PAGE. After pCMB treatment of the subcomplex, the heme subunit recovered from PAGE showed a large autoxidizability, even with 2-mercaptoethanol treatment. Addition of cholate repressed this autoxidizability after 2-mercaptoethanol treatment. These results suggest that the stable binding of the hinge protein to the heme subunit is essential for the non-autoxidizability of the cytochrome C1 subcomplex, and that cysteinyl residues in the subcomplex must be involved to a certain extent in the stable binding between the two subunits.
KeywordsStable Binding Sephadex Column Cysteinyl Residue Millimolar Extinction Coefficient Redox Carrier
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