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Proc Natl Acad Sci U S A. 2017 Jun 27;114(26):6866-6871. doi: 10.1073/pnas.1705689114. Epub 2017 Jun 12.

A recruiting protein of geranylgeranyl diphosphate synthase controls metabolic flux toward chlorophyll biosynthesis in rice.

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State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210023, China.
State Key Laboratory of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Division of Plant and Soil Sciences, West Virginia University, Morgantown, WV 26505.
State Key Laboratory of Crop Genetics and Germplasm Enhancement, Research Center of Jiangsu Plant Gene Engineering, Nanjing Agricultural University, Nanjing 210095, China.
State Key Laboratory of Hybrid Rice, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
Department of Biochemistry, Purdue University, West Lafayette, IN 47907
State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210023, China;


In plants, geranylgeranyl diphosphate (GGPP) is produced by plastidic GGPP synthase (GGPPS) and serves as a precursor for vital metabolic branches, including chlorophyll, carotenoid, and gibberellin biosynthesis. However, molecular mechanisms regulating GGPP allocation among these biosynthetic pathways localized in the same subcellular compartment are largely unknown. We found that rice contains only one functionally active GGPPS, OsGGPPS1, in chloroplasts. A functionally active homodimeric enzyme composed of two OsGGPPS1 subunits is located in the stroma. In thylakoid membranes, however, the GGPPS activity resides in a heterodimeric enzyme composed of one OsGGPPS1 subunit and GGPPS recruiting protein (OsGRP). OsGRP is structurally most similar to members of the geranyl diphosphate synthase small subunit type II subfamily. In contrast to members of this subfamily, OsGRP enhances OsGGPPS1 catalytic efficiency and specificity of GGPP production on interaction with OsGGPPS1. Structural biology and protein interaction analyses demonstrate that affinity between OsGRP and OsGGPPS1 is stronger than between two OsGGPPS1 molecules in homodimers. OsGRP determines OsGGPPS1 suborganellar localization and directs it to a large protein complex in thylakoid membranes, consisting of geranylgeranyl reductase (OsGGR), light-harvesting-like protein 3 (OsLIL3), protochlorophyllide oxidoreductase (OsPORB), and chlorophyll synthase (OsCHLG). Taken together, genetic and biochemical analyses suggest OsGRP functions in recruiting OsGGPPS1 from the stroma toward thylakoid membranes, thus providing a mechanism to control GGPP flux toward chlorophyll biosynthesis.


chlorophyll biosynthesis; geranylgeranyl diphosphate synthase; protein complex formation; rice; terpenoids

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