TY - JOUR
T1 - Structural basis for enzymatic photocatalysis in chlorophyll biosynthesis
AU - Zhang, Shaowei
AU - Heyes, Derren J.
AU - Feng, Lingling
AU - Sun, Wenli
AU - Johannissen, Linus O.
AU - Liu, Huanting
AU - Levy, Colin W.
AU - Li, Xuemei
AU - Yang, Ji
AU - Yu, Xiaolan
AU - Lin, Min
AU - Hardman, Samantha J. O.
AU - Hoeven, Robin
AU - Sakuma, Michiyo
AU - Hay, Sam
AU - Leys, David
AU - Rao, Zihe
AU - Zhou, Aiwu
AU - Cheng, Qi
AU - Scrutton, Nigel S.
PY - 2019/10/23
Y1 - 2019/10/23
N2 - The enzyme protochlorophyllide oxidoreductase (POR) catalyses a light-dependent step in chlorophyll biosynthesis that is essential to photosynthesis and, ultimately, all life on Earth1,2,3. POR, which is one of three known light-dependent enzymes4,5, catalyses reduction of the photosensitizer and substrate protochlorophyllide to form the pigment chlorophyllide. Despite its biological importance, the structural basis for POR photocatalysis has remained unknown. Here we report crystal structures of cyanobacterial PORs from Thermosynechococcus elongatus and Synechocystis sp. in their free forms, and in complex with the nicotinamide coenzyme. Our structural models and simulations of the ternary protochlorophyllide–NADPH–POR complex identify multiple interactions in the POR active site that are important for protochlorophyllide binding, photosensitization and photochemical conversion to chlorophyllide. We demonstrate the importance of active-site architecture and protochlorophyllide structure in driving POR photochemistry in experiments using POR variants and protochlorophyllide analogues. These studies reveal how the POR active site facilitates light-driven reduction of protochlorophyllide by localized hydride transfer from NADPH and long-range proton transfer along structurally defined proton-transfer pathways.
AB - The enzyme protochlorophyllide oxidoreductase (POR) catalyses a light-dependent step in chlorophyll biosynthesis that is essential to photosynthesis and, ultimately, all life on Earth1,2,3. POR, which is one of three known light-dependent enzymes4,5, catalyses reduction of the photosensitizer and substrate protochlorophyllide to form the pigment chlorophyllide. Despite its biological importance, the structural basis for POR photocatalysis has remained unknown. Here we report crystal structures of cyanobacterial PORs from Thermosynechococcus elongatus and Synechocystis sp. in their free forms, and in complex with the nicotinamide coenzyme. Our structural models and simulations of the ternary protochlorophyllide–NADPH–POR complex identify multiple interactions in the POR active site that are important for protochlorophyllide binding, photosensitization and photochemical conversion to chlorophyllide. We demonstrate the importance of active-site architecture and protochlorophyllide structure in driving POR photochemistry in experiments using POR variants and protochlorophyllide analogues. These studies reveal how the POR active site facilitates light-driven reduction of protochlorophyllide by localized hydride transfer from NADPH and long-range proton transfer along structurally defined proton-transfer pathways.
U2 - 10.1038/s41586-019-1685-2
DO - 10.1038/s41586-019-1685-2
M3 - Article
VL - 574
SP - 722
EP - 725
JO - Nature: international weekly journal of science
JF - Nature: international weekly journal of science
SN - 0028-0836
ER -