Open AccessSpecific binding of victorin to a 100-kDa protein from oats
Author(s) -
T. Wolpert,
V. Macko
Publication year - 1989
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.86.11.4092
Subject(s) - biology , in vivo , locus (genetics) , binding protein , biochemistry , receptor , toxin , in vitro , genotype , plasma protein binding , cytosol , microbiology and biotechnology , genetics , enzyme , gene
Susceptibility of oats to victoria blight, caused by the fungusCochliobolus victoriae , and sensitivity to the host-specific toxin victorin, produced by the fungus, are controlled by the dominant allele at theVb locus. It has been postulated that theVb locus encodes a toxin receptor, although direct evidence for such a receptor is not available. Our recent studies on structure—activity relationships of the toxin established a methodology for producing125 I-labeled victorin. Electrophoretic analysis of proteins from isogenic susceptible and resistant oat genotypes following treatment of leaves with radiolabeled victorin showed that victorin binds in a covalent and a genotype-specific manner to a 100-kDa protein only in susceptible oat leaf slices. Thisin vivo binding was competitively displaced by reduced victorin, a nontoxic protective compound, and appeared to be correlated with biological activity.In vitro binding to the 100-kDa protein in leaf extracts showed several differences fromin vivo binding. Binding was not genotype specific and required a reducing agent that was not required forin vivo binding. Differential centrifugation showed that the 100-kDa victorin binding protein was not a cytosolic protein but was enriched in a high-speed particulate fraction. The data support the hypothesis that the 100-kDa protein is the victorin receptor.