Evolution of the cytochromeb gene of mammals |
| |
Authors: | David M Irwin Thomas D Kocher Allan C Wilson |
| |
Institution: | (1) Division of Biochemistry and Molecular Biology, University of California, 94720 Berkeley, CA, USA;(2) Present address: Department of Zoology, University of New Hampshire, 03824 Durham, NH, USA |
| |
Abstract: | Summary With the polymerase chain reaction (PCR) and versatile primers that amplify the whole cytochromeb gene (∼ 1140 bp), we obtained 17 complete gene sequences representing three orders of hoofed mammals (ungulates) and dolphins
(cetaceans). The fossil record of some ungulate lineages allowed estimation of the evolutionary rates for various components
of the cytochromeb DNA and amino acid sequences. The relative rates of substitution at first, second, and third positions within codons are
in the ratio 10 to 1 to at least 33. For deep divergences (>5 million years) it appears that both replacements and silent
transversions in this mitochondrial gene can be used for phylogenetic inference. Phylogenetic findings include the association
of (1) cetaceans, artiodactyls, and perissodactyls to the exclusion of elephants and humans, (2) pronghorn and fallow deer
to the exclusion of bovids (i. e., cow, sheep, and goat), (3) sheep and goat to the exclusion of other pecorans (i. e., cow,
giraffe, deer, and pronghorn), and (4) advanced ruminants to the exclusion of the chevrotain and other artiodactyls. Comparisons
of these cytochromeb sequences support current structure-function models for this membrane-spanning protein. That part of the outer surface which
includes the Qo redox center is more constrained than the remainder of the molecule, namely, the transmembrane segments and the surface that
protrudes into the mitochondrial matrix. Many of the amino acid replacements within the transmembrane segments are exchanges
between hydrophobic residues (especially leucine, isoleucine, and valine). Replacement changes at first and second positions
of codons approximate a negative binomial distribution, similar to other protein-coding sequences. At four-fold degenerate
positions of codons, the nucleotide substitutions approximate a Poisson distribution, implying that the underlying mutational
spectrum is random with respect to position. |
| |
Keywords: | Polymerase chain reaction Direct sequencing Mitochondrial DNA Hoofed mammals Cetaceans Molecular phylogeny Evolutionary rates Base composition Structure-function relationships |
本文献已被 SpringerLink 等数据库收录! |
|