C-Phycocyanin from Mastigocladus laminosus. Isolation and Properties of Subunits and, Small Aggregates

PHOTOCHEMISTRY OF PHYCOBILIPROTEINS: RECIPROCITY OF REVERSIBLE PHOTOCHEMISTRY AND AGGREGATION IN PHYCOERYTHROCYANIN FROMMastigocladus laminosus

“…In native PC, the photochemistry is inhibited probably by rigid fixation of the chromophores, as witnessed by the high fluorescence yield (Scheer, 1982). Only in the region where this fixation is Loosened, but the influence of the protein not yet fully removed, is a photochemical Z-to-E isomerization possible (John et al, 1985). This situation probably corresponds to the one in which the structurally very similar chromophore of phytochrome is present in the native chromoprotein.…”

“…In no case has their been conclusive evidence, however, that the phycochromes are indeed the putative photoreceptors. The situation became even more complex by reports of several groups that phycobiliproteins can be induced to photochemistry reminiscent of these phycochromes by mild denaturation in vitro (deKok et al, 1981;John et al, 1985;Murakami and Fujita, 1983;Ohad et al,1980;Ohki and Fujita, 1979a;Schmidt et al, 1988) or photobleaching in vivo (Ohki and Fujita, 1979b). In at least one case, it has furthermore been shown that such mild denaturation treatments can change the aggregation equilibrium from tri-to monomeric (Murakami and Fujita, 1983), e.g.…”

FÖRSTER TRANSFER CALCULATIONS BASED ON CRYSTAL STRUCTURE DATA FROM Agmenellum quadruplicatum C‐PHYCOCYANIN

“…Conflicting spectroscopic results have been discussed by John et al (1985). Mimuro et al (1986) have suggested that p84 is the chromophore absorbing at longer wavelength, and this assignment has been verified by titration of PC with cysteine-modifying reagents (Siebzehnriibl et al, 1987).…”

“…Whereas the absorption (and CD) spectra of the subunits add up to that of the monomer (Mimuro et al, 1986;John er al., 1985;Switalski and Sauer, 1985), red shifts on the order of 6 nm occur in PC from M . laminosus (Mimuro et al, 1986;John et al, 1985) upon trimerization, which have been neglected in the calculations. The crystallographic data have been collected for molecules that are trimeric (Mastigocladus laminosus) or hexameric (Agmenellum quadruplicatum) in their most stable forms.…”

ORIGIN OF THE RED SHIFTED ABSORPTION IN PHYCOCYANIN 632 FROM Mastigocladus laminosus

“…There are several "families" of linker polypeptides in the 10, 30 and 90 kDa range (Bryant, 1988;Rumbeli and Zuber, 1988;Gantt, 1986;Morschel et al, 1977), which bind specifically to individual biliproteins, and occupy specific locations within the phycobilisome. In connection with spectroscopic studies on red-shifted PC species isolated from extracts of the cyanobacterium Mastigocladus laminosus, we had indirect evidence that unusual linker polypeptide(s) migrating with an apparent MW around 22 kDa were correlated with the most redshifted species (John et al, 1985;John, 1986;Fisher, 1985;Wendler et al, 1986;Schneider et al, 1988). For a better characterization, we have now devised an isolation method using mildly denaturing conditions throughout, determined the N-terminal sequence, and performed reconstruction experiments with PC from the same organism.…”