Modulating the proteinase inhibitory profile of a plant cystatin by single mutations at positively selected amino acid sites

Cysteine proteinase inhibitors of the cystatin superfamily have several important functions in plants, including the inhibition of exogenous cysteine proteinases during herbivory or infection. Here we used a maximum-likelihood approach to assess whether plant cystatins, like other proteins implicate...

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Bibliographic Details
Published in:	The Plant journal : for cell and molecular biology Vol. 48; no. 3; pp. 403 - 413
Main Authors:	Kiggundu, Andrew, Goulet, Marie-Claire, Goulet, Charles, Dubuc, Jean-François, Rivard, Daniel, Benchabane, Meriem, Pépin, Geneviève, Vyver, Christell van der, Kunert, Karl, Michaud, Dominique
Format:	Journal Article
Language:	English
Published:	Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.11.2006 Blackwell Publishing Ltd Blackwell Science
Subjects:	Agronomy. Soil science and plant productions Amino Acids Amino Acids - chemistry Base Sequence binding properties Binding sites Biological and medical sciences cathepsin B cathepsin H chemistry Codon cystatins Cystatins - chemistry Cystatins - pharmacology Cysteine Proteinase Inhibitors Cysteine Proteinase Inhibitors - pharmacology DNA Primers evolution Flowers & plants functional diversity Fundamental and applied biological sciences. Psychology Genetics and breeding of economic plants Herbivory Likelihood Functions Lycopersicon esculentum Models, Molecular Mutagenesis mutants Mutation papain pharmacology Plant breeding: fundamental aspects and methodology plant cystatins plant–insect interactions Poaceae positive selection Proteinase inhibitors Proteins site-directed mutagenesis Solanaceae Tomatoes Cystatin EC 3.4.22.16 Monocotyledones Cysteine plant cystatins Pest cysteine proteinase inhibitors Gramineae plant-insect interactions Dicotyledones Aminoacid Angiospermae Lycopersicon esculentum site- directed mutagenesis Spermatophyta EC 3.4.22.1 positive selection Inhibition Mutation Solanaceae EC 3.4.22.2
ISSN:	0960-7412, 1365-313X
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Summary:	Cysteine proteinase inhibitors of the cystatin superfamily have several important functions in plants, including the inhibition of exogenous cysteine proteinases during herbivory or infection. Here we used a maximum-likelihood approach to assess whether plant cystatins, like other proteins implicated in host-pest interactions, have been subject to positive selection during the course of their evolution. Several amino acid sites were identified as being positively selected in cystatins from either Poaceae (monocots) and Solanaceae (dicots). These hypervariable sites were located at strategic positions on the protein: on each side of the conserved glycine residues in the N-terminal trunk, within the first and second inhibitory loops entering the active site of target enzymes, and surrounding the [smallcapital larfav] motif, a sequence of unknown function conserved among plant cystatins. Supporting the assumption that positively selected, hypervariable sites are indicative of amino acid sites implicated in functional diversity, mutants of the 8th cystatin unit of tomato multicystatin including alternative residues at positively selected sites in the N-terminal trunk exhibited highly variable affinities for the cysteine proteases papain, cathepsin B and cathepsin H. Overall, these observations support the hypothesis that plant cystatins have been under selective pressure to evolve in response to predatory challenges by herbivorous enemies. They also indicate the potential of site-directed mutagenesis at positively selected sites for the generation of cystatins with improved binding properties.
Bibliography:	http://dx.doi.org/10.1111/j.1365-313X.2006.02878.x This is an intra‐laboratory collaboration. The first four authors contributed equally to this work. SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 14 ObjectType-Article-1 ObjectType-Feature-2 content type line 23
ISSN:	0960-7412 1365-313X
DOI:	10.1111/j.1365-313X.2006.02878.x