Effect of Monoclonal Antibodies on the in Vitro P_<FR> Dark Reversion of Pea Phytochrome

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Extraction as P_<FR> and immunoaffinity chromatography yielded a pea phytochrome sample with polypeptide size of 121 kdalton, the same as in a crude extract which was immediately heated in SDS. A difference spectrum was almost the same as that observed in etiolated pea epicotyls except that ΔA_<666>/ΔA_<730> of 1.20 was significantly larger. At 10℃ dark reversion from P_<FR> occurred, with the decrease in A_<728> being almost equal to the increase in A_<667>. The kinetics could be resolved into three first-order components, the major, slow component accounting for more than 90% of the absorbance changes. In the presence of monoclonal anti-pea phytochrome antibodies mAP-1, 3 or 5, which bind away from the chromophore, and mAP-7, which binds near the chromophore, the rate of the major component was reduced at either one or both wavelengths. None of these antibodies affected the absorption spectra of phytochrome. In the presence of mAP-9, which is suggested to bind near the amino-terminus, the absorption at the red-light-induced photostationary state was reduced and the rate of dark reversion was increased, resembling partially degraded phytochrome of 114 kdalton, but with no evidence of proteolysis.
日本植物生理学会の論文