Open AccessSelective Binding of [ 3 H]Gibberellin A 1 by Protein Fractions from Dwarf Pea Epicotyls
Author(s) -
J. L. Stoddart,
William Breidenbach,
Ronn Nadeau,
Lawrence Rappaport
Publication year - 1974
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.71.8.3255
Subject(s) - gibberellin , sephadex , metabolite , chemistry , biochemistry , biology , botany , enzyme
A homogenate from dwarf pea seedlings that had been treated with [3 H]gibberellin A1 was separated by Sephadex G-200 into two protein fractions, of high and intermediate molecular weight, with affinity for [3 H]gibberellin A1 . Neither fraction bound [3 H]gibberellin A8 , the only metabolite of [3 H]gibberellin A1 detected in significant quantity in extracts of pea seedlings. These proteinhormone complexes were noncovalently bound, as evidenced by their rapid disruption in ethanol. Approximate molecular weights of the fractions were 500,000 and 60,000. In experiments designed to detect competition for the binding proteins between [3 H]gibberellin A1 and closely related [3 H]gibberellin molecules, [3 H]gibberellin A8 and pseudo [3 H]gibberellin A1 were inactive, but keto [3 H]gibberellin competed favorably. Equilibrium dialysis experiments revealed that both high-molecular-weight and intermediate-molecular-weight protein-hormone complexes could undergo hormone exchange with nonlabeled gibberellin A1 .