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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The transport of spermidine into a cyanobacterium, Synechocystis sp. PCC 6803, was characterized by measuring the uptake of 14C-spermidine. Spermidine transport was shown to be saturable with an apparent affinity constant (Km) value of 67 microM and a maximal velocity (Vmax) value of 0.45 nmol/min/mg protein. Spermidine uptake was pHdependent with the pH optimum being 8.0. The competition experiment showed strong inhibition of spermidine uptake by putrescine and spermine, whereas amino acids were hardly inhibitory. The inhibition kinetics of spermidine transport by putrescine and spermine was found to be noncompetitive with Ki values of 292 and 432 microM, respectively. The inhibition of spermidine transport by various metabolic inhibitors and ionophores suggests that spermidine uptake is energy-dependent. The diminution of cell growth was observed in cells grown at a high concentration of NaCl. Addition of a low concentration of spermidine at 0.5 mM relieved growth inhibition by salt stress. Upshift of the external osmolality generated by either NaCl or sorbitol caused an increased spermidine transport with about 30- 40% increase at 10 mosmol/kg upshift.
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PMID:Characterization of spermidine transport system in a cyanobacterium,synechocystis sp. PCC 6803. 1949 91

To investigate the short term effect of ultraviolet (UV) radiations on changes in pigments and polyamine contents, Synechocystis sp. PCC 6803 cells after exposure to UV-radiation were extracted by dimethylformamide and perchloric acid for pigments and polyamines determination, respectively. Cell growth was slightly decreased after 1 h exposure to UV-A and UV-B radiations. UV-C had little effect on cell growth despite the decrease of photosynthetic rate by about 18%. UV-A and UV-B decreased the contents of chlorophyll a and carotenoids whereas UV-C decreased chlorophyll a but had no effect on carotenoids. Spermidine contents were unaffected by UV-A, in contrast to the reduction of 25 and 50% by UV-B and UV-C, respectively. All three types of UV-radiation particularly reduced perchloric acid-insoluble spermidine. Importantly, putrescine and spermine which accounted for less than 1% of intracellular polyamines were increased by about three- to eight-fold by UV-B and UV-C, respectively. The changes in polyamines contents by UV-B and UV-C were consistent with the changes in transcript levels of arginine decarboxylase mRNA, but not with the protein levels. The decrease in the transcripts of adc2 but not adc1 was observed with UV-B and UV-C treatments.
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PMID:Short-term UV-B and UV-C radiations preferentially decrease spermidine contents and arginine decarboxylase transcript levels of Synechocystis sp. PCC 6803. 2068 Feb 81