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

Area of Science:

• Plant Biochemistry
• Molecular Biology
• Protein Chemistry

Background:

• Cytokinins are essential plant hormones regulating growth and development.
• Understanding cytokinin-binding proteins is crucial for elucidating hormone signaling pathways.

Purpose of the Study:

• To isolate and characterize a cytokinin-binding protein from wheat germ.
• To determine the binding affinity of the isolated protein to various cytokinin analogs.

Main Methods:

• Ammonium sulfate precipitation and carboxymethyl Sephadex chromatography for initial protein purification.
• Affinity chromatography using a kinetin riboside derivative for specific isolation.
• Sephadex G-200 gel filtration to estimate molecular weight.
• Equilibrium dialysis to determine binding constants.

Main Results:

• A cytokinin-binding protein was successfully isolated from wheat germ.
• The protein has an estimated molecular weight of 122,000 daltons.
• High affinity was observed for kinetin (Kd = 1.2 µM), N(6)-benzylaminopurine, and N(6)-(Delta(2)-isopentenyl)adenine.
• Low binding affinity was found for cis-zeatin and trans-zeatin.

Conclusions:

• Wheat germ contains a specific cytokinin-binding protein with a preference for adenine-based cytokinins.
• This protein may play a role in cytokinin perception or transport in plants.
• Further studies are warranted to elucidate the precise function of this protein in vivo.