Comparative biochemistry, hemoglobin

Rendell, M., P M. Stephen, R. Paulsen, J. L. Valentine, K. Rasbold, T. Hestorff, S. Eastberg, and D. C. Shint. 1985. An interspecies comparison of normal levels of glycosylated hemoglobin and glycosylated albumin. Comparative Biochemistry and Physiology 818 819-822. 

A very intriguing aspect of comparative biochemistry is the comparison of dissociation curves of hemoglobin (as a function of decreasing oxygen tension) with the general behavior of the corresponding animal species. 

Cytochrome c (see 2 and Fig. 2-7) in the mitochondria is part of the chain of electron carrier proteins that ultimately produce ATP from ADP (oxidative phosphorylation). In principle, the heme in cytochrome c is the same as that in hemoglobin. But in detail, the vinyl groups, after conversion to thioethers, are covalently linked to cysteine amino residues of the protein chain [2,5]. The fifth coordination site of iron is occupied again by the imidazole N-atom of a histidine, but the sixth position is now coordinated to the S-atom of a methionine (Figs. 2-7, 2-17). The redox potential of low-spin Fe(III)/Fe(II) with E°= +0.25 V vs. NHE is drastically altered compared to heme. Now this heme iron is much more able to act in the electron-transporting chain by redox cycling. The mechanisms of electron transfer are available in modem textbooks of biochemistry. It is interesting to note that the macromolecular protein chain... 

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