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Novel gene products associated with NdhD3/D4‐containing NDH‐1 complexes are involved in photosynthetic CO 2 hydration in the cyanobacterium, Synechococcus sp. PCC7942
Author(s) -
Maeda Shinichi,
Badger Murray R.,
Price G. Dean
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.02753.x
Subject(s) - thylakoid , biology , cyanobacteria , photosynthesis , electron transport chain , carbonic anhydrase , synechococcus , biochemistry , photosystem ii , photosystem i , mutant , nadh dehydrogenase , chloroplast , gene , dehydrogenase , function (biology) , biophysics , enzyme , microbiology and biotechnology , bacteria , genetics , protein subunit
Summary Cyanobacteria possess light‐dependent CO 2 uptake activity that results in the net hydration of CO 2 to HCO 3 – and may involve a protein‐mediated carbonic anhydrase (CA)‐like activity. This process is vital for the survival of cyanobacteria and may be a contributing factor in the ecological success of this group of organisms. Here, via isolation of mutants of Synechococcus sp. PCC7942 that cannot grow under low‐CO 2 conditions, we have identified two novel genes, chpX and chpY , that are involved in light‐dependent CO 2 hydration and CO 2 uptake reactions; co‐inactivation of both these genes abolished both activities. The function and mechanism of the CO 2 uptake systems supported by each chp gene product differs, with each associated with functionally distinct NAD(P)H dehydrogenase (NDH‐1) complexes. The ChpX system has a low affinity for CO 2 and is de‐pendent on photosystem I cyclic electron transport, whereas the inducible ChpY system has a high affinity for CO 2 and is dependent on linear electron transport. We believe that ChpX and ChpY are involved in a unique, net hydration of CO 2 to HCO 3 – , that is coupled electron flow within the NDH‐1 complex on the thylakoid membrane.