Evolution and Protein Structure - II

Cytochrome is a single polypeptide chain of about 104 residues:

Horse Cytochrome C (1hrc)

Comparison of cytochrome c from a large number of species:

The sequences are remarkably similar across species, especially at certain positions.

The implication is that the strongly conserved residues contribute significantly to the structure and function of the protein.

Other positions contribute very little and are highly variable; evolutionary drift randomizes these residues.

Note that human and chimpanzee sequences are identical, and macaque and spider monkey are very similar to the human/chimpanzee sequence. This implies a common and relatively recent evolutionary divergence.

Backbone alignment likewise shows similarities:

Backbone Alignment of Horse Cytochrome C (1hrc) with Tuna Cytochrome C (5cyt)
RMSD = 0.47 Å

A useful way to present these similarities and differences is to draw an evolutionary tree [Schwartz and Dayhoff, Science, 1978, 199, 395]:


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