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Molecular modeling and inhibitory activity of cowpea cystatin against bean bruchid pests
Author(s) -
Aguiar Juliana M.,
Franco Octávio L.,
Rigden Daniel J.,
Bloch Carlos,
Monteiro Ana C.S.,
Flores Victor M.Q.,
Jacinto Tânia,
XavierFilho José,
Oliveira Antonia E.A.,
GrossideSá Maria F.,
Fernandes Kátia V.S.
Publication year - 2006
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.20901
Subject(s) - vigna , cystatin , biology , papain , callosobruchus maculatus , cysteine , biochemistry , botany , enzyme , cystatin c , pest analysis , renal function
Plant cystatins show great potential as tools to genetically engineer resistance of crop plants against pests. Two important potential targets are the bean weevils Acanthoscelides obtectus and Zabrotes subfasciatus , which display major activities of digestive cysteine proteinases in midguts. In this study a cowpea cystatin, a cysteine proteinase inhibitor found in cowpea ( Vigna unguiculata ) seeds, was expressed in Escherichia coli and purified with a Ni‐NTA agarose column. It strongly inhibited papain and proteinases from midguts of both A. obtectus and Z. subfasciatus bruchids, as seen by in vitro assays. When the protein was incorporated into artificial seeds at concentrations as low as 0.025%, and seeds were consumed by the bruchids larva, dramatic reductions in larval weight, and increases in insect mortality were observed. Molecular modeling studies of cowpea cystatin in complex with papain revealed that five N‐terminal residues responsible for a large proportion of the hydrophobic interactions involved in the stabilization of the enzyme–inhibitor complex are absent in the partial N‐terminal amino acid sequencing of soybean cystatin. We suggest that this structural difference could be the reason for the much higher effectiveness of cowpea cystatin when compared to that previously tested phytocystatin. The application of this knowledge in plant protein mutation programs aiming at enhancement of plant defenses to pests is discussed. Proteins 2006. © 2006 Wiley‐Liss, Inc.