Resolution of the subunit composition of a cytokinin-binding protein from wheat embryos

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Abstract
When the wheat germ cytokinin-binding protein (CBF-1) is isolated from excised wheat embryos only one group of polypeptides near 54 000 is observed as opposed to three polypeptide groups reported for CBF-1 from commercially milled wheat germ. The other two lower molecular mass polypeptide groups previously reported are probably proteolytic degradation products of the 54 000 species resulting from excessive heat or physical damage during milling. The CBF-1 polypeptide accumulates rapidly in the embryo after 20 days post-anthesis. A larger set of polypeptides near 66 000 – 68 000 appears during embryo development and also reacts with anti-CBF-1 serum. These polypeptides are also observed upon immunoprecipitation of 20-day embryo polyadenylated RNA translation products although the data are not definitive enough to prove a precursor relationship to the CBF-1 54 000 polypeptide. The new findings are discussed in regard to previous characterizations of CBF-1.