The defensins consist of two independent, convergent protein superfamilies
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journal contribution
posted on 2020-12-18, 00:38 authored by Thomas Shafee, FT Lay, MD Hulett, MA Anderson© 2016 The Author. The defensin and defensin-like proteins are an extensive group of small, cationic, disulfide-rich proteins found in animals, plants, and fungi and mostly perform roles in host defense. The term defensin was originally used for small mammalian proteins found in neutrophils and was subsequently applied to insect proteins and plant γ-thionins based on their perceived sequence and structural similarity. Defensins are often described as ancient innate immunity molecules and classified as a single superfamily and both sequence alignments and phylogenies have been constructed. Here, we present evidence that the defensins have not all evolved from a single ancestor. Instead, they consist of two analogous superfamilies, and extensive convergent evolution is the source of their similarities. Evidence of common origin necessarily gets weaker for distantly related genes, as is the case for defensins, which are both divergent and small. We show that similarities that have been used as evidence for common origin are all expected by chance in short, constrained, disulfide-rich proteins. Differences in tertiary structure, secondary structure order, and disulfide bond connectivity indicate convergence as the likely source of the similarity. We refer to the two evolutionarily independent groups as the cis-defensins and trans-defensins based on the orientation of the most conserved pair of disulfides.
Funding
This study was supported by the Australian Research Council (Grant number 150104386) and Hexima Ltd.
Australian Research Council | 150104386
Hexima Ltd.
History
Publication Date
2016-09-01Journal
Molecular Biology and EvolutionVolume
33Issue
9Pagination
12p. (p. 2345-2356)Publisher
Oxford University PressISSN
0737-4038Rights Statement
The Author reserves all moral rights over the deposited text and must be credited if any re-use occurs. Documents deposited in OPAL are the Open Access versions of outputs published elsewhere. Changes resulting from the publishing process may therefore not be reflected in this document. The final published version may be obtained via the publisher’s DOI. Please note that additional copyright and access restrictions may apply to the published version.Publisher DOI
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Science & TechnologyLife Sciences & BiomedicineBiochemistry & Molecular BiologyEvolutionary BiologyGenetics & Hereditydefensintoxingamma-thioninconvergent evolutionevolutionary constraintantimicrobial peptidestructural homologyANTIMICROBIAL PEPTIDESPLANT DEFENSINSHUMAN BETA-DEFENSIN-1STRUCTURAL-PROPERTIESTHETA-DEFENSINSEVOLUTIONALPHAHOMOLOGYFAMILIESGENESAnimalsHumansDrosophila melanogasterDefensinsSequence AlignmentEvolution, MolecularPhylogenyAmino Acid SequenceProtein Structure, SecondarySequence Homology, Amino AcidStructure-Activity RelationshipModels, MolecularBiological Evolutionstructural homology.
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