Cyt. c evolves quite slowly in most organisms and is very stable in
its conformation and function, as evidenced by the ability to form stable,
functional complexes of cyt. c and cyt. c oxidase between eukaryotes and
prokaryotes. However, mammals do show some rate heterogeneity and
functional changes. See Baba et al. 1981. J. Mol. Evol. 17:197-213 and
Cann et al. 1984. Genetics 104:699-711 for evidence on the rate changes.
See Osheroff et al. 1983. J. Biol. Chem. 258:5731-5738 for evidence that
the physical interaction between cyt. c and cyt. c oxidase has changed in
higher primates.
You should keep in mind that the mouse and rat and the two snakes
you list are very close relatives of each other. Also, baleen whales are
close relatives of artiodacyls. In fact artiodactyla may be paraphyletic
with whales falling inside the order. I think Dan Graur has a recent paper
on this.
Ron Adkins
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Ronald Adkins adkins at hgc.sph.uth.tmc.edu
Human Genetics Center, SPH 713-792-4624 (Tel)
University of Texas 713-792-4615 (FAX)
P.O. Box 20334
Houston, TX 77225
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