Photosynthetic electron transport involved in PxcA-dependent proton extrusion in Synechocystis sp. strain PCC6803: Effect of pxcA inactivation on CO2, HCO3-, and NO3- uptake

Masatoshi Sonoda, Hirokazu Katoh, Willem Vermaas, George Schmetterer, Teruo Ogawa

Research output: Contribution to journalArticle

29 Scopus citations

Abstract

The product of pxcA (formerly known as cotA) is involved in light- induced Na+-dependent proton extrusion. In the presence of 2,5-dimethyl-p- benzoquinone, net proton extrusion by Synechocystis sp. strain PCC6803 ceased after 1 min of illumination and a postillumination influx of protons was observed, suggesting that the PxcA-dependent, light-dependent proton extrusion equilibrates with a light-independent influx of protons. A photosystem I (PS I) deletion mutant extruded a large number of protons in the light. Thus, PS II-dependent electron transfer and proton translocation are major factors in light-driven proton extrusion, presumably mediated by ATP synthesis. Inhibition of CO2 fixation by glyceraldehyde in a cytochrome c oxidase (COX) deletion mutant strongly inhibited the proton extrusion. Leakage of PS II-generated electrons to oxygen via COX appears to be required for proton extrusion when CO2 fixation is inhibited. At pH 8.0, NO3- uptake activity was very low in the pxcA mutant at low [Na+] (~100 μM). At pH 6.5, the pxcA strain did not take up CO2 or NO3- at low [Na+] and showed very low CO2 uptake activity even at 15 mM Na+. A possible role of PxcA-dependent proton exchange in charge and pH homeostasis during uptake of CO2, HCO3-, and NO3- is discussed.

Original languageEnglish (US)
Pages (from-to)3799-3803
Number of pages5
JournalJournal of bacteriology
Volume180
Issue number15
DOIs
StatePublished - Aug 1998

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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