Species Distribution
Cytochrome c is a highly conserved protein across the spectrum of species, found in plants, animals, and many unicellular organisms. This, along with its small size (molecular weight about 12,000 daltons), makes it useful in studies of cladistics. Its primary structure consists of a chain of about 100 amino acids. Many higher order organisms possess a chain of 104 amino acids.
The cytochrome c molecule has been studied for the glimpse it gives into evolutionary biology. Both chickens and turkeys have identical sequence (amino acid for amino acid), whereas ducks possess molecules differing by one amino acid. Similarly, both humans and chimpanzees have the identical molecule, while rhesus monkeys share all but one of the amino acids: the 66th amino acid is isoleucine in the former and threonine in the latter. Pigs, cows and sheep also share identical cytochrome c molecules.
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