Protein taxonomic relationships between

When scientists examine the primary structures of proteins that carry out the same function in different organisms, they can correlate the number of amino acid differences in the proteins to the closeness of the taxonomic relationship between the species. For exarr5)le, c)h ochrome c, a protein that transfers electrons in biological oxidations, has about 100 amino acids. Yeast cytochrome c differs by 48 amino acids from horse cytochrome c, whereas duck cytochrome c differs by only two amino acids from chicken cytochrome c. Ducks and chickens, therefore, have a much closer taxonomic relationship than horses and yeast. Likewise, the cytochrome c in chickens and turkeys have identical primary structures. Human cytochrome c and chimpanzee cytochrome c are also identical and differ by one amino acid from the C54ochrome c of the rhesus monkey. 

A sensitive probe of electrostatic interactions in the distal pocket is provided by the structural and vibrational properties of the Fe-CO unit [9], The bound CO ligand exhibits three main infrared (IR) absorption bands, denoted Ao, A, and A3, with vibrational frequencies 1965 cm-1, 1949 cm, and 1933 cm, respectively. These bands, which change relative intensity and wave-number depending on temperature, pressure, pH, or solvent [10], are used to identify functionally different conformational substrates of MbCO, denoted taxonomic substates [11], Nevertheless the relationship between the A states and specific structural features of the protein has not yet been clarified. 

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