Novel insights on the mechanism of action of α-amylase inhibitors from the plant defensin family

• Published in: Proteins, structure, function, and bioinformatics structure, function, and bioinformatics, 2008-11, Vol.73 (3), p.719-729
• Main Authors: Pelegrini, Patrícia B., Lay, Fung T., Murad, André M., Anderson, Marilyn A., Franco, Octavio L.
• Format: Article
• Language: English
• Subjects: alpha-Amylases - antagonists & inhibitors; Amino Acid Sequence; Animals; Base Sequence; Chromatography, High Pressure Liquid; cloning; Cloning, Molecular; cowpea; defensin; Defensins - chemistry; Defensins - genetics; Defensins - isolation & purification; Defensins - metabolism; DNA, Plant - genetics; Electrophoresis, Polyacrylamide Gel; Enzyme Inhibitors - chemistry; Enzyme Inhibitors - isolation & purification; Enzyme Inhibitors - metabolism; expression; Fabaceae - metabolism; Humans; Insecta - enzymology; Models, Molecular; Molecular Sequence Data; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - isolation & purification; Plant Proteins - metabolism; Protein Structure, Secondary; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - metabolism; Seeds - metabolism; Sequence Alignment; α-amylase
• ISSN: 0887-3585; 1097-0134
• DOI: 10.1002/prot.22086

Plant defensins are small cysteine‐rich proteins commonly synthesized in plants, encoded by large multigene families. Most plant defensins that have been characterized to date show potent antifungal and/or bactericidal activities. This report describes VuD1, an unusual defensin that is able to inhibit insect‐pest α‐amylases. VuD1 was cloned from cowpea (Vigna unguiculata) seeds and expressed in a heterologous system. Inhibitory enzyme assays showed that VuD1 efficiently inhibits α‐amylases from the weevils Acanthoscelides obtectus and Zabrotes subfasciatus, caused low inhibition toward mammalian enzymes and was unable to inhibit the α‐amylases from Callosobruchus maculatus and Aspergillus fumigatus. To shed some light over the mechanism of action of VuD1, molecular modeling analyses were performed, revealing that the N‐terminus of the molecule is responsible for binding with the active site of weevil enzymes. Moreover, models of VuD1 and mammalian enzymes were also generated to elucidate the specificity mechanisms. The data presented herein suggests that this defensin has potential application in the development of transgenic plants for insect pest control. Proteins 2008. © 2008 Wiley‐Liss, Inc.