TY - JOUR
T1 - Arginine residues in the D2 polypeptide may stabilize bicarbonate binding in photosystem II of Synechocystis sp. PCC 6803
AU - Cao, Jiancheng
AU - Vermaas, Willem
AU - Govindjee,
N1 - Funding Information:
We are thankful to Beth Eggers for her help in the site-directed mutagenesis and Paul Jursinic for his help in the measurements and analyses of oxygen evolution in a sequence of flashes. This study has been supported by the Interdisciplinary McKnight Grant to the University of Illinois at Urbana-Champaign (J.C. and G.) and NSF grant DCB90-19248 to W.V. Govindjee thanks the Center for Advanced Studies at UIUC for Associate Membership during the fall semester of 1989 and the Arizona State University for a Visiting Professorship in 1990.
PY - 1991/8/23
Y1 - 1991/8/23
N2 - Bicarbonate (HCO3-) causes a significant and reversible stimulation of anion-inhibited electron flow in photosystem II of higher plants and cyanobacteria. To test if selected arginine (Arg) residues are involved in the binding of HCO3-, we utilized oligonucleotide-directed mutagenesis to construct Synechocystis sp. PCC 6803 mutants carrying mutations in Arg residues in the D2 protein. Measurements of oxygen evolution showed that the D2 mutants R233Q (arginine-233 → glutamine) and R251S (arginine-251 → serine) were 10-fold more sensitive to formate than the wild type. The formate concentration giving half-maximal inhibition of the steady-state oxygen evolution rate was 48 mM, 4.5 mM and 4 mM for the wild type, R233Q and R251S, respectively. Measurements of oxygen evolution in single-turnover flashes confirm that the mutants are more sensitive to formate than the wild type. Measurements of chlorophyll a fluorescence decay kinetics after the second saturating actinic flash indicated that, after formate treatment, the halftime of QA- oxidation was decreased by approximately a factor of 2, 4 and 6 in the wild type, R251S and R233Q, respectively. The recombination rate between QA- and S2 was approx. 2-fold slower in R251S and R233Q than in the wild type. In the presence of 100 mM sodium formate, reactivation of the Hill reaction by bicarbonate showed that the wild type had an apparent Km for bicarbonate of 0.5 mM, while the Km values for R233Q and R251S were 1.4 and 1.5 mM, respectively. We suggest that Arg-233 and Arg-251 in the D2 polypeptide contribute to stabilization of HCO3- binding in Photosystem II.
AB - Bicarbonate (HCO3-) causes a significant and reversible stimulation of anion-inhibited electron flow in photosystem II of higher plants and cyanobacteria. To test if selected arginine (Arg) residues are involved in the binding of HCO3-, we utilized oligonucleotide-directed mutagenesis to construct Synechocystis sp. PCC 6803 mutants carrying mutations in Arg residues in the D2 protein. Measurements of oxygen evolution showed that the D2 mutants R233Q (arginine-233 → glutamine) and R251S (arginine-251 → serine) were 10-fold more sensitive to formate than the wild type. The formate concentration giving half-maximal inhibition of the steady-state oxygen evolution rate was 48 mM, 4.5 mM and 4 mM for the wild type, R233Q and R251S, respectively. Measurements of oxygen evolution in single-turnover flashes confirm that the mutants are more sensitive to formate than the wild type. Measurements of chlorophyll a fluorescence decay kinetics after the second saturating actinic flash indicated that, after formate treatment, the halftime of QA- oxidation was decreased by approximately a factor of 2, 4 and 6 in the wild type, R251S and R233Q, respectively. The recombination rate between QA- and S2 was approx. 2-fold slower in R251S and R233Q than in the wild type. In the presence of 100 mM sodium formate, reactivation of the Hill reaction by bicarbonate showed that the wild type had an apparent Km for bicarbonate of 0.5 mM, while the Km values for R233Q and R251S were 1.4 and 1.5 mM, respectively. We suggest that Arg-233 and Arg-251 in the D2 polypeptide contribute to stabilization of HCO3- binding in Photosystem II.
KW - (Synechocystis sp. PCC 6803)
KW - Bicarbonate effect
KW - Cyanobacterium
KW - D2 polypeptide
KW - Photosystem II
KW - Site-directed mutagenesis
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U2 - 10.1016/S0005-2728(05)80202-6
DO - 10.1016/S0005-2728(05)80202-6
M3 - Article
C2 - 1909178
AN - SCOPUS:0025739048
VL - 1059
SP - 171
EP - 180
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
SN - 0005-2728
IS - 2
ER -