Skip to main content
padlock icon - secure page this page is secure

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

Download Article:
 Download
(PDF 307.7 kb)
 
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 thelarfavmotif, 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.
No References
No Citations
No Supplementary Data
No Article Media
No Metrics

Keywords: cysteine proteinase inhibitors; plant cystatins; plant–insect interactions; positive selection; site-directed mutagenesis

Document Type: Research Article

Affiliations: 1: Centre de Recherche en Horticulture & Institut des Nutraceutiques et des Aliments Fonctionnels, Pavillon des Services/INAF, Université Laval, QC, Canada G1K 7P4 2: Forestry and Agricultural Biotechnology Institute, Botany Department, University of Pretoria, Pretoria 0002, South Africa

Publication date: November 1, 2006

  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
X
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more