The effects of nitrogen and sulfur limitation on various cellular parameters of the cyanobacterium Synechococcus 6301 were studied by electron microscopy, morphometry and biochemical methods. Nitrate and sulfate starvation for 70 h results in a massive glycogen accumulation in parallel to a loss of soluble protein and chlorophyll. Phycobilisomes disappear prior to the degradation of photosynthetic membranes. For sulfate-starved cells, a formation of “storage granules” (poly-β-hydroxy-butyric acid) is typical which amount up to 10% of the cell volume. The composition of polar lipids is simple: equal parts of C 16:0 and C 16:1 are present under all nutritional conditions; their amount is directly correlated with the total cellular membrane area as deter­mined by morphometry. Nitrate starved cells regenerate almost completely in structure and composition within 9 h after nitrate supplementation. Regeneration of sulfate starved cells is retarded; in spite of significant synthesis of phycocyanin within 9 h the cells still exhibit marked signs of starvation.

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The cyanobacterium Synechococcus 6301 is able to use a limited number of sulfur compounds as the only source of sulfur supply such as sulfate, thiosulfate, thioacetic acid, mercaptoacetic acid, thioacetamide, ʟ-cysteine and glutathione. Compounds containg thioether linkages such as methionin or S-methylcysteine and all compounds investigated so far containing sulfonic acid structures do not support growth. Growth inhibiton was observed by addition of aminomethane- sulfonic acid or cysteamine.When non-growth sustaining sulfur compounds are added as sulfur source, the C-phycocyanin content of the Synechococcus cultures decreased drastically, causing a shift in color from blue- green to yellow-green. An analysis reveals the degradation of C-phycocyanin whereas chlorophyll formation still proceeds to a certain degree in growing sulfur-starved cells. Supplementation of a suitable sulfur source induces a period of intense and preferential C-phycocyanin synthesis prior to resumption of normal growth.

Abbauversuche an neun verschiedenen Biliproteiden zeigen, daR immer jeweils Ring A des Chrornophors und einer der mittleren Ringe (bei Phycoerythrinen als Ring C identifiziert) mit dem Protein kovalent verknupft sind. Nach Spektraluntersuchungen besitzt der Chromophor des Phycoerythrins sechs, der des Phycocyanins neun konjugierte Doppelbindungen. Bei der Abspaltung der Chromophore mit siedendem Methanol kommt jeweils eine Doppelbindung hinzu. Fur den Phycoerythrin-Chromophor wird aufgrund der Kinetik der Isomerisierung in ein Urobilin die Teilstruktur 11 vorgeschlagen, die die Bindungsstelle zum Protein berucksichtigt. Bonding between Chromophore and Protein in Biliproteins, 1. -Degradation Experiments and Spectral Investigations on BiliproteinsDegradation experiments with nine different biliproteins show that ring A of the chromophore and one of the middle rings (in phycoerythrin identified as ring C) are always covalently linked with the apoprotein. According to spectral investigations, the chrornophore of phycoerythrin contains six, and that of phycocyanin nine conjugated double bonds. One additional double bond is formed during splitting of the chromophore with boiling methanol. Partial structure 11 containing the linkage to the apoprotein is proposed for the phycoerythrin chromophore on the basis of kinetics of isomerization to a urobilin.Phycocyanine und Phycoerythrine 1) -die photosynthetisch aktiven Biliproteide von Rot-, Blaualgen und Cryptornonolesenthalten kovalent gebundene Chromophore (blau: Phycocyanobilin, rot: Phycoerythrobilin). Uber die kovalenten Bindungen zwischen den Chromophoren und. dem Protein-Anteil in den verschiedenen Biliproteiden gibt es bisher widerspruchliche, z. T. spekulative Angaben.Aufgrund der Spaltungsgeschwindigkeit bei saurer Hydrolyse wird einerseits fur C-Phycocyanin 2 ) und fur B-Phycoerythrin3) eine Esterbindung, andererseits fur C-und Allophyco-*) Korrespondenz bitte an diesen Autor richten.

Red algae of the species Porphyridium cruentum were grown in a minimum sulfate medium containing 3sS02-. 35S-labeled phycoerythrin was extracted. B Phycoerythrin, b phycoerythrin and R phycocyanin could be separated from other proteins by using a carrier-free electrophoresis on columns. The final ratio A s~s / A~~o of B phycoerythrin thus obtained was >, 5.3sS-labeled B phycoerythrin was digested proteolytically with trypsin and pepsin. The resulting 3sS-containing bilipeptides were separated by isoelectric focusing. Zones of enhanced chromophore concentration always showed an enhanced radioactivity.Peptide fractions with a low molar ratio sulfur/chromophore (1.1 -1.8) were purified to remove sucrose and the carrier ampholyte. A modified, optimized Edman degradation followed. A butylacetate-soluble, red Edman product was obtained that contained most of the chromophore and the bulk of the radioactivity. This product was purified by two-dimensional thin-layer chromatography. The main spot of the chromatogram was subjected to acidic hydrolysis. The major part of the radioactivity in the hydrolysate cochromatographed with cysteine. That proves cysteine to be the binding amino acid in all cases investigated.