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.