Why Are The Cytochrome C Sequences Different?
Cytochrome c performs the same function in all organisms. It is found in the mitochondria (except in the prokaryotic bacteria) and is a part of the electron transport system which functions in aerobic respiration. Cytochrome c accepts electrons from a complex built into the mitochondrial membrane called cytochrome reductase and gives up the electrons to another complex, cytochrome oxidase (Dickerson, 1980). It consists of a chain of 104 amino acids folded into a three-dimensional structure bound to a heme group. Although there are differences in the sequence of amino acids in the various organisms (see Dayhoff, 1969; Dickerson, 1972; Dickerson, 1980 for the actual sequences), all versions have the same three-dimensional shape, even the cytochrome c from humans and Neurospora which differ in 44 of the 104 positions. To further illustrate the functional equivalence of all these versions of cytochrome c, the cytochrome c from any organism reacts equally well in the test tube with the cyto
