Structural and functional studies of a phosphatidic acid-binding antifungal plant defensin MtDef4: Identification of an RGFRRR motif governing fungal cell entry

Journal Article · Wed Dec 04 04:00:00 EST 2013 · PLoS One, 8(12):e82485

DOI:https://doi.org/10.1371/journal.pone.0082485· OSTI ID:1115824

Sagaram, Uma S.; El-Mounadi, Kaoutar; Buchko, Garry W.; Berg, Howard R.; Kaur, Jagdeep; Pandurangi, Raghoottama; Smith, Thomas J.; Shah, Dilip

A highly conserved plant defensin MtDef4 potently inhibits the growth of a filamentous fungus Fusarium graminearum. MtDef4 is internalized by cells of F. graminearum. To determine its mechanism of fungal cell entry and antifungal action, NMR solution structure of MtDef4 has been determined. The analysis of its structure has revealed a positively charged patch on the surface of the protein consisting of arginine residues in its γ-core signature, a major determinant of the antifungal activity of MtDef4. Here, we report functional analysis of the RGFRRR motif of the γ-core signature of MtDef4. The replacement of RGFRRR to AAAARR or to RGFRAA not only abolishes fungal cell entry but also results in loss of the antifungal activity of MtDef4. MtDef4 binds strongly to phosphatidic acid (PA), a precursor for the biosynthesis of membrane phospholipids and a signaling lipid known to recruit cytosolic proteins to membranes. Mutations of RGFRRR which abolish fungal cell entry of MtDef4 also impair its binding to PA. Our results suggest that RGFRRR motif is a translocation signal for entry of MtDef4 into fungal cells and that this positively charged motif likely mediates interaction of this defensin with PA as part of its antifungal action.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1115824
• Report Number(s): PNNL-SA-90528; 47398
• Journal Information: PLoS One, 8(12):e82485, Journal Name: PLoS One, 8(12):e82485
• Country of Publication: United States
• Language: English

Related Subjects

Environmental Molecular Sciences Laboratory
NMR spectroscopy
antifungal agent
defensins
membrane dynamics
structural biology