TY - JOUR
T1 - Role of PsbV-Tyr137 in photosystem II studied by site-directed mutagenesis in the thermophilic cyanobacterium Thermosynechococcus vulcanus
AU - Xiao, Yanan
AU - Zhu, Qingjun
AU - Yang, Yanyan
AU - Wang, Wenda
AU - Kuang, Tingyun
AU - Shen, Jian Ren
AU - Han, Guangye
N1 - Funding Information:
This work was supported by National Key R&D Program of China (2017YFA0503700); National Natural Science Foundation of China (31470339); A Strategic Priority Research Program of CAS (XDB17000000); A Key Research Program of Frontier Sciences, CAS, Grant No.QYZDY-SSW-SMC003.
Funding Information:
This work was supported by National Key R&D Program of China (2017YFA0503700); National Natural Science Foundation of China (31470339); A Strategic Priority Research Program of CAS (XDB17000000); A Key Research Program of Frontier Sciences, CAS, Grant No.QYZDY-SSW-SMC003.
Publisher Copyright:
© 2020, Springer Nature B.V.
PY - 2020/4/27
Y1 - 2020/4/27
N2 - PsbV (cytochrome c550) is one of the three extrinsic proteins of photosystem II (PSII) and functions to maintain the stability and activity of the Mn4CaO5 cluster, the catalytic center for water oxidation. PsbV-Y137 is the C-terminal residue of PsbV and is located at the exit of a hydrogen-bond network mediated by the D1-Y161-H190 residue pair. In order to examine the function of PsbV-Y137, four mutants, PsbV-Y137A, PsbV-Y137F, PsbV-Y137G, and PsbV-Y137W, were generated with Thermosynechococcus vulcanus (T. vulcanus). These mutants showed growth rates similar to that of the wild-type strain (WT); however, their oxygen-evolving activities were different. At pH 6.5, the oxygen evolution rates of Y137F and Y137W were almost identical to that of WT, whereas the oxygen evolution rates of the Y137A, Y137G mutants were 64% and 61% of WT, respectively. However, the oxygen evolution in the latter two mutants decreased less at higher pHs, suggesting that higher pHs facilitated oxygen evolution probably by facilitating proton egress in these two mutants. Furthermore, thylakoid membranes isolated from the PsbV-Y137A, PsbV-Y137G mutants exhibited much lower levels of oxygen-evolving activity than that of WT, which was found to be caused by the release of PsbV. In addition, PSII complexes purified from the PsbV-Y137A and PsbV-Y137G mutants lost all of the three extrinsic proteins but instead bind Psb27, an assembly cofactor of PSII. These results demonstrate that the PsbV-Tyr137 residue is required for the stable binding of PsbV to PSII, and the hydrogen-bond network mediated by D1-Y161-H190 is likely to function in proton egress during water oxidation.
AB - PsbV (cytochrome c550) is one of the three extrinsic proteins of photosystem II (PSII) and functions to maintain the stability and activity of the Mn4CaO5 cluster, the catalytic center for water oxidation. PsbV-Y137 is the C-terminal residue of PsbV and is located at the exit of a hydrogen-bond network mediated by the D1-Y161-H190 residue pair. In order to examine the function of PsbV-Y137, four mutants, PsbV-Y137A, PsbV-Y137F, PsbV-Y137G, and PsbV-Y137W, were generated with Thermosynechococcus vulcanus (T. vulcanus). These mutants showed growth rates similar to that of the wild-type strain (WT); however, their oxygen-evolving activities were different. At pH 6.5, the oxygen evolution rates of Y137F and Y137W were almost identical to that of WT, whereas the oxygen evolution rates of the Y137A, Y137G mutants were 64% and 61% of WT, respectively. However, the oxygen evolution in the latter two mutants decreased less at higher pHs, suggesting that higher pHs facilitated oxygen evolution probably by facilitating proton egress in these two mutants. Furthermore, thylakoid membranes isolated from the PsbV-Y137A, PsbV-Y137G mutants exhibited much lower levels of oxygen-evolving activity than that of WT, which was found to be caused by the release of PsbV. In addition, PSII complexes purified from the PsbV-Y137A and PsbV-Y137G mutants lost all of the three extrinsic proteins but instead bind Psb27, an assembly cofactor of PSII. These results demonstrate that the PsbV-Tyr137 residue is required for the stable binding of PsbV to PSII, and the hydrogen-bond network mediated by D1-Y161-H190 is likely to function in proton egress during water oxidation.
KW - Extrinsic proteins
KW - Hydrogen-bond network
KW - Photosystem II
KW - PsbV
KW - Site-directed mutagenesis
KW - Water-splitting
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U2 - 10.1007/s11120-020-00753-8
DO - 10.1007/s11120-020-00753-8
M3 - Article
C2 - 32342261
AN - SCOPUS:85084214800
VL - 146
SP - 41
EP - 54
JO - Photosynthesis Research
JF - Photosynthesis Research
SN - 0166-8595
IS - 1-3
ER -