title: Effects of Phosphorylation of β Subunits of Phycocyanins on State Transition in the Model Cyanobacterium Synechocystis sp. PCC 6803.
abstract: Synechocystis sp. PCC 6803 (hereafter Synechocystis) is a model cyanobacterium and has been used extensively for studies concerned with photosynthesis and environmental adaptation. Although dozens of protein kinases and phosphatases with specificity for Ser/Thr/Tyr residues have been predicted, only a few substrate proteins are known in Synechocystis. In this study, we report 194 in vivo phosphorylation sites from 149 proteins in Synechocystis, which were identified using a combination of peptide pre-fractionation, TiO(2) enrichment and liquid chromatograpy-tandem mass spectrometry (LC-MS/MS) analysis. These phosphorylated proteins are implicated in diverse biological processes, such as photosynthesis. Among all identified phosphoproteins involved in photosynthesis, the β subunits of phycocyanins (CpcBs) were found to be phosphorylated on Ser22, Ser49, Thr94 and Ser154. Four non-phosphorylated mutants were constructed by using site-directed mutagenesis. The in vivo characterization of the cpcB mutants showed a slower growth under high light irradiance and displayed fluorescence quenching to a lower level and less efficient energy transfer inside the phycobilisome (PBS). Notably, the non-phosphorylated mutants exhibited a slower state transition than the wild type. The current results demonstrated that the phosphorylation status of CpcBs affects the energy transfer and state transition of photosynthesis in Synechocystis. This study provides novel insights into the molecular mechanisms of protein phosphorylation in the regulation of photosynthesis in cyanobacteria and may facilitate the elucidation of the entire regulatory network by linking kinases to their physiological substrates.
authors: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, Hubei, China These authors contributed equally to this work. wangqiang@ihb.ac.cn gefeng@ihb.ac.cn.
authors: Zhuo
authors: Z
authors: Chen
authors: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, Hubei, China University of Chinese Academy of Sciences, Beijing 100094, China These authors contributed equally to this work. wangqiang@ihb.ac.cn gefeng@ihb.ac.cn.
authors: Jiao
authors: J
authors: Zhan
authors: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, Hubei, China wangqiang@ihb.ac.cn gefeng@ihb.ac.cn.
authors: Ying
authors: Y
authors: Chen
authors: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, Hubei, China wangqiang@ihb.ac.cn gefeng@ihb.ac.cn.
authors: Mingkun
authors: M
authors: Yang
authors: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, Hubei, China wangqiang@ihb.ac.cn gefeng@ihb.ac.cn.
authors: Chenliu
authors: C
authors: He
authors: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, Hubei, China wangqiang@ihb.ac.cn gefeng@ihb.ac.cn.
authors: Feng
authors: F
authors: Ge
authors: Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, Hubei, China wangqiang@ihb.ac.cn gefeng@ihb.ac.cn.
authors: Qiang
authors: Q
authors: Wang
mesh_terms: D010766:Phosphorylation / Q000502:physiology; D010788:Photosynthesis / Q000502:physiology; D010798:Phycocyanin / Q000737:chemistry / Q000378:metabolism*; D046939:Synechocystis / Q000378:metabolism*
chemical_list: D010798:Phycocyanin
keywords: Phosphoproteomics; Photosynthesis; State transition; Synechocystis sp. PCC 6803; TiO2 enrichment; β subunits of phycocyanins (CpcBs)