Affinity labeling of Avena phytochrome with ATP analogs

AUTOR(ES)

Wong, Yum-Shing

RESUMO

The presence of ATP-dependent, polycation-stimulated protein kinase activity in highly purified phytochrome preparations [Wong, Y.-S., Cheng, H.-C., Walsh, D. A. & Lagarias, J. C. (1986) J. Biol. Chem. 261, 12089-12097] has renewed the hypothesis that the phytochrome photoreceptor possesses enzymatic activity. A prerequisite for protein kinase function is the presence of an ATP binding site. Here we present evidence for a nucleoside triphosphate binding site(s) in the phytochrome molecule. Two ATP analogs, 5′-p-fluorosulfonylbenzoyladenosine and 8-azidoadenosine 5′-triphosphate, were used to affinity label purified Avena phytochrome. Labeling with both reagents is stimulated by the polycations poly(Lys75,Ala25) and histone H1. Coincubation with ATP inhibits the polycation-stimulated labeling of phytochrome. In similar experiments GTP, CTP, UTP, ADP, and pyrophosphate, but not adenosine or AMP, also prevent photoaffinity labeling of phytochrome.

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