Characterization of monoclonal antibodies to oat phytochrome by competitive radioimmunoassays and comparative immunoblots of phytochrome peptides

Light-induced import of the chromoprotein, phytochrome, into mitochondria

Mitochondria extracted from plants that were irradiated with actinic light in vivo have associated with them the chromoprotein, phytochrome. This phytochrome retains its native subunit size of 124 kDa after proteolytic treatment of the mitochondria with trypsin and chymotrypsin. This result suggests that phytochrome is not exposed on the outer surface of the outer mitochondrial membrane. Phytochrome, so protected, is not found to be associated with mitochondria derived from unirradiated plants. The possibility that the photoactivation of phytochrome induces a conformational change in its structure which facilitates its transport into the mitochondrion is discussed.

Site-directed antisera to the chromophore binding site of phytochrome: characterization and cross-reactivity

The preparation and characterization of antisera to a synthetic undecapeptide which encompasses the chromophore binding site on oat phytochrome are described. By direct enzyme-linked immunosorbent assay, this antiserum recognizes bilin-linked peptides in proteolytic digestion mixtures of phytochrome from several plant species including the monocot species, oat and maize, and the dicot species, pea. Competitive enzyme-linked immunosorbent assays have been used to establish the specificity of the site-directed antisera for those peptides homologous with the synthetic undecapeptide which are present in complex mixtures. These results show that the local environment of the phytochromobilin prosthetic group is structurally conserved.