Open AccessAbsence of the psbH gene product destabilizes photosystem II complex and bicarbonate binding on its acceptor side in Synechocystis PCC 6803
Author(s) -
Komenda Josef,
Lupínková Lenka,
Kopecký Jiří
Publication year - 2002
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1046/j.0014-2956.2001.02693.x
Subject(s) - synechocystis , chemistry , photosystem ii , protein subunit , mutant , wild type , biochemistry , bicarbonate , gene , photosynthesis , organic chemistry
The PsbH protein, a small subunit of the photosystem II complex (PSII), was identified as a 6‐kDa protein band in the PSII core and subcore (CP47–D1–D2–cyt b ‐559) from the wild‐type strain of the cyanobacterium Synechocystis PCC 6803. The protein was missing in the D1–D2–cytochrome b ‐559 complex and also in all PSII complexes isolated from IC7, a mutant lacking the psbH gene. The following properties of PSII in the mutant contrasted with those in wild‐type: (a) CP47 was released during nondenaturing electrophoresis of the PSII core isolated from IC7; (b) depletion of CO 2 resulted in a reversible decrease of the␣ reoxidation rate in the IC7 cells; (c) light‐induced decrease in PSII activity, measured as 2,5–dimethyl‐benzoquinone‐supported Hill reaction, was strongly dependent on the HCO 3 – concentration in the IC7 cells; and (d) illumination of the IC7 cells lead to an extensive oxidation, fragmentation and cross‐linking of the D1 protein. We did not find any evidence for phosphorylation of the PsbH protein in the wild‐type strain . The results showed that in the PSII complex of Synechocystis attachment of CP47 to the D1–D2 heterodimer appears weakened and binding of bicarbonate on the PSII acceptor side is destabilized in the absence of the PsbH protein.