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Characterization of the antimicrobial peptide family defensins in the Tasmanian devil (Sarcophilus harrisii), koala (Phascolarctos cinereus), and tammar wallaby (Macropus eugenii)

Authors
  • Jones, Elizabeth A.1
  • Cheng, Yuanyuan1
  • O’Meally, Denis1, 2
  • Belov, Katherine1
  • 1 University of Sydney, Faculty of Veterinary Science, School of Life and Environmental Sciences, Camperdown, NSW, 2006, Australia , Camperdown (Australia)
  • 2 University of the Sunshine Coast, Centre for Animal Health Innovation, Sippy Downs, QLD, 4556, Australia , Sippy Downs (Australia)
Type
Published Article
Journal
Immunogenetics
Publisher
Springer-Verlag
Publication Date
Nov 12, 2016
Volume
69
Issue
3
Pages
133–143
Identifiers
DOI: 10.1007/s00251-016-0959-1
Source
Springer Nature
Keywords
License
Yellow

Abstract

Defensins comprise a family of cysteine-rich antimicrobial peptides with important roles in innate and adaptive immune defense in vertebrates. We characterized alpha and beta defensin genes in three Australian marsupials: the Tasmanian devil (Sarcophilus harrisii), koala (Phascolarctos cinereus), and tammar wallaby (Macropus eugenii) and identified 48, 34, and 39 defensins, respectively. One hundred and twelve have the classical antimicrobial peptides characteristics required for pathogen membrane targeting, including cationic charge (between 1+ and 15+) and a high proportion of hydrophobic residues (>30%). Phylogenetic analysis shows that gene duplication has driven unique and species-specific expansions of devil, koala, and tammar wallaby beta defensins and devil alpha defensins. Defensin genes are arranged in three genomic clusters in marsupials, whereas further duplications and translocations have occurred in eutherians resulting in four and five gene clusters in mice and humans, respectively. Marsupial defensins are generally under purifying selection, particularly residues essential for defensin structural stability. Certain hydrophobic or positively charged sites, predominantly found in the defensin loop, are positively selected, which may have functional significance in defensin-target interaction and membrane insertion.

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