| Abstract: | Almost all of the particulate phytochrome of maize coleoptiles,obtained by cross-linking phytochrome to its putative receptormembrane by glutaraldehyde within the intact cells, sedimentedduring relatively low-speed centrifugation (10 000-20 000 g).The sediment contained morphologically identifiable mitochondria,some microsomes, plasma membranes, and membranes whose originis not yet known. Although its density was very similar to thatof mitochondria the phytochrome-containing material sedimentedseparately from mitochondria and microsomes but roughly in parallelwith an oligomycin-insensitive ATP-hydrolysing activity. Enrichmentof the phytochrome-containing material was obtained by subfractionationof the 20 000 g sediment. This enrichment of phytochrome coincidedwith an enrichment of certain vesicles, which, on the basisof their staining properties, are taken to be plasma membranevesicles, in the subfraction. The evidence is held to supportthe view that phytochrome attaches to and interacts with theplasma membrane upon photo transformation to the Pfr1 form. |
