Evolutionary diversification of the mammalian defensins

Authors
Citation
Al. Hughes, Evolutionary diversification of the mammalian defensins, CELL MOL L, 56(1-2), 1999, pp. 94-103
Citations number
35
Categorie Soggetti
Cell & Developmental Biology
Journal title
CELLULAR AND MOLECULAR LIFE SCIENCES
ISSN journal
1420682X → ACNP
Volume
56
Issue
1-2
Year of publication
1999
Pages
94 - 103
Database
ISI
SICI code
1420-682X(19991001)56:1-2<94:EDOTMD>2.0.ZU;2-O
Abstract
Defensins are cysteine-rich cationic peptides that function in antimicrobia l defense in both invertebrates and vertebrates. Three main groups of anima l defensins are known: insect defensins; mammalian alpha-defensins and vert ebrate beta-defensins. It has been difficult to determine whether these mol ecules are homologous or have independently evolved similar features, but o verall the evidence favors a distant relationship. The best evidence of thi s relationship is structural, particularly from their overall three-dimensi onal structure and from the spacing of half-cystine residues involved in in tra-chain disulfide bonds. Some evidence favors a closer relationship betwe en vertebrate beta-defensins and insect defensins than between the two grou ps of vertebrate defensins. Examination of nucleotide substitutions between recently duplicated mammalian defensin genes shows that the rate of nonsyn onymous (amino-acid-altering) substitution exceeds that of synonymous subst itution in the region of the gene encoding the mature defensin. This highly unusual pattern of nucleotide substitution is evidence that natural select ion has acted to diversify defensins at the amino acid level. The resulting rapid evolution explains why it is difficult to reconstruct the evolutiona ry history of these molecules.