Active Transport of CO2 by the Cyanobacterium Synechococcus UTEX 625 : Measurement by Mass Spectrometry

摘要: Mass spectrometry has been used to confirm the presence of an active transport system for CO(2) in Synechococcus UTEX 625. Cells were incubated at pH 8.0 100 micromolar KHCO(3) absence Na(+) (to prevent HCO(3) (-) transport). Upon illumination cells rapidly removed almost all free from medium. Addition carbonic anhydrase revealed that depletion resulted a selective uptake CO(2), rather than total inorganic carbon species. stopped (<3 seconds) when light was turned off. Iodoacetamide (3.3 millimolar) completely inhibited fixation but had little effect on transport. In iodoacetamide poisoned cells, occurred against concentration gradient about 18,000 1. Transport by 10 diethylstilbestrol, membrane-bound ATPase inhibitor. Studies with DCMU and PSI indicated driven ATP produced cyclic or pseudocyclic photophosphorylation. Low concentrations (<100 microequivalents per liter), not K(+), stimulated as much 2.4-fold. Unlike Na(+)-dependent transport, high (30 milliequivalents liter) Li(+). During illumination, medium remained far below its equilibrium value periods up 15 minutes. This could only happen if continuously occurring rapid rate, since continuing dehydration would raise ceased. Measurement rate dissolved accumulation under these conditions least part balanced efflux.