Inhibition of trypsin by cowpea thionin: Characterization, molecular modeling, and docking

Abstract

Higher plants produce several families of proteins with toxic properties, which act as defense compounds against pests and pathogens. The thionin family represents one family and comprises low molecular mass cysteine-rich proteins, usually basic and distributed in different plant tissues. Here, we report the purification and characterization of a new thionin from cowpea (Vigna unguiculata) with proteinase inhibitory activity. Cowpea thionin inhibits trypsin, but not chymotrypsin, binding with a stoichiometry of 1:1 as shown with the use of mass spectrometry. Previous annotations of thionins as proteinase inhibitors were based on their erroneous identification as homologues of Bowman-Birk family inhibitors. Molecular modeling experiments were used to propose a mode of docking of cowpea thionin with trypsin. Consideration of the dynamic properties of the cowpea thionin was essential to arrive at a model with favorable interface characteristics comparable with structures of trypsin-inhibitor complexes determined by X-ray crystallography. In the final model, Lys11 occupies the S1 specificity pocket of trypsin as part of a canonical style interaction.

Multidimensional signatures in antimicrobial peptides

“…The botanical literature indicates many of these peptides are plant defense molecules (20,21). Moreover, the plant proteinase inhibitor superfamily includes thionins (22) that contain a ␥-core motif as defined herein (Table 1). These observations substantiate congruence between the ␥-core structural motif and functional correlates in related host defense peptides (17,23).…”

Effect of trypsin inhibitor from Crotalaria pallida seeds on Callosobruchus maculatus (cowpea weevil) and Ceratitis capitata (fruit fly)

“…These plant proteinaceous inhibitors are generally small, stable and abundant proteins [21] showing specificity for serine proteinase, cysteine proteinase, aspartic proteinase or metallo-proteinases [17]. Serine proteinase inhibitors are found in plant storage tissues, such as seeds, tubers, leaves and fruits [13,22]. Most of these inhibitors bind to cognate enzymes according to a common substrate-like canonical mechanism [17].…”

Isolation and Properties of Floral Defensins from Ornamental Tobacco and Petunia

“…Thevissen andcolleagues (1996, 2000) have suggested that the defensin initiates this response by interaction with a membrane-bound receptor rather than by permeabilizing the membrane by direct defensin-lipid interaction. Certain members within the plant defensin family also display other biological activities, including proteinase (Wijaya et al, 2000;Melo et al, 2002) and ␣-amylase (Bloch and Richardson, 1991;Zhang et al, 1997) inhibitory activity and inhibition of protein translation (Colilla et al, 1990;Mendez et al, 1990; that may contribute to their role in defense.…”