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Crystal structure of rice defensin OsAFP1 and molecular insight into lipid-binding.

Authors
  • Ochiai, Akihito1
  • Ogawa, Kodai2
  • Fukuda, Minami2
  • Suzuki, Masami2
  • Ito, Kosuke3
  • Tanaka, Takaaki4
  • Sagehashi, Yoshiyuki5
  • Taniguchi, Masayuki4
  • 1 Department of Materials Science and Technology, Faculty of Engineering, Niigata University, Niigata 950-2181, Japan; Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan. Electronic address: [email protected] , (Japan)
  • 2 Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan. , (Japan)
  • 3 Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan; Department of Biology, Faculty of Science, Niigata University, Niigata 950-2181, Japan. , (Japan)
  • 4 Department of Materials Science and Technology, Faculty of Engineering, Niigata University, Niigata 950-2181, Japan; Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan. , (Japan)
  • 5 Hokkaido Agricultural Research Center, National Agriculture and Food Research Organization (NARO), Hokkaido 062-8555, Japan. , (Japan)
Type
Published Article
Journal
Journal of Bioscience and Bioengineering
Publisher
Elsevier
Publication Date
Jul 01, 2020
Volume
130
Issue
1
Pages
6–13
Identifiers
DOI: 10.1016/j.jbiosc.2020.02.011
PMID: 32192842
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Defensins are antibacterial peptides that function in the innate immune system. OsAFP1, a defensin identified from Oryza sativa (rice), exhibits antimicrobial activity against rice pathogens. Intriguingly, OsAFP1 was also shown to demonstrate potent antifungal activity against the human pathogenic fungus Candida albicans by inducing apoptosis in target cells, suggesting that OsAFP1 represents a potential new antibiotic candidate; however, further analyses, particularly at the structural level, are required to elucidate the mechanistic underpinnings of OsAFP1 antifungal activity. Here, we determined the three-dimensional structure of OsAFP1 using X-ray crystallography. OsAFP1 features the cysteine-stabilized αβ structure highly conserved in plant defensins and presents a dimeric structure that appears necessary for antifungal activity. Superimposition of the OsAFP1 structure with that of Nicotiana alata NaD1 complexed with phosphatidic acid indicated that the target molecule is likely trapped between the S2-S3 loops of each OsAFP1 dimer. In lipid-binding analyses performed using nitrocellulose membranes immobilized with various membrane lipid components, OsAFP1 was found to bind to phosphatidylinositols (PIPs) harboring phosphate groups, particularly PI(3)P. These results indicate that OsAFP1 exerts antifungal activity by binding to PI(3)P contained in the C. albicans cell membrane, thereby applying cellular stress and inducing apoptosis. Furthermore, the OsAFP1 structure and site-specific-mutation analyses revealed that Arg1, His2, Leu4, Arg9, and Phe10 play critical roles in OsAFP1 dimer formation. Thus, our study provides novel insights into the antifungal mechanism of OsAFP1. Copyright © 2020 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

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