Variations in the amino acid composition of cyanophycin in the cyanobacterium Synechocystis sp. PCC 6308 as a function of growth conditions.
Gas chromatography-mass spectrometry studies of the nitrogen isotopic composition of the N-trifluoroacetyl n-butyl ester derivatives of the amino acids from isolated hydrolyzed cyanophycin from 15N-enriched cells led to two major findings: (1) the amino acid composition of this granular polypeptide, isolated using procedures optimized for extracting and purifying cyanophycin from cells in the stationary growth phase, varied with the culture growth condition; (2) the rate of incorporation of exogenous nitrate differed for each nitrogen atom of the amino acid constituents of cyanophycin or cyanophycin-like polypeptide. Arginine and aspartic acid were the principle components of cyanophycin isolated from exponentially growing cells and from light-limited stationary phase cells, with glutamic acid as an additional minor component. The cyanophycin-like polypeptide from nitrogen-limited cells contained only aspartic and glutamic acids, but no arginine. The glutamic acid content decreased and arginine content increased as nitrate was provided to nitrogen-limited cells. These cells rapidly incorporated nitrate at different rates at each cyanophycin nitrogen site: guanidino nitrogens of arginine > aspartic acid > alpha-amino nitrogen of arginine > glutamic acid. Little media-derived nitrogen was incorporated into cyanophycin of exponentially growing cells during one cellular doubling time.
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Department of Chemistry, Wellesley College, MA 02181.
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D000596:Amino Acids / Q000032:analysis*; D001120:Arginine / Q000032:analysis; D001224:Aspartic Acid / Q000032:analysis; D001426:Bacterial Proteins; D000458:Cyanobacteria / Q000737:chemistry* / Q000254:growth & development; D008401:Gas Chromatography-Mass Spectrometry; D018698:Glutamic Acid / Q000032:analysis; D009587:Nitrogen Isotopes; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification
D000596:Amino Acids; D001426:Bacterial Proteins; D009587:Nitrogen Isotopes; D010940:Plant Proteins; C024250:cyanophycin; D001224:Aspartic Acid; D018698:Glutamic Acid; D001120:Arginine