A Cytokinin-binding Protein from Wheat Germ: Isolation by Affinity Chromatography and Properties

A cytokinin-binding protein has been isolated from wheat germ via ammonium sulfate precipitation, carboxymethyl Sephadex chromatography, and affinity chromatography on a column substituted with a derivative of kinetin riboside. On Sephadex G-200, the protein migrated with an apparent molecular weight of 122,000 daltons. The dissociation constant for kinetin was determined by equilibrium dialysis to be 1.2 micromolar; N⁶-benzylaminopurine and N⁶-(Δ²-isopentenyl)adenine were also strongly bound. Little affinity was exhibited toward either cis-zeatin or trans-zeatin.