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Structural basis of light-induced redox regulation in the Calvin-Benson cycle in cyanobacteria

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Title: Structural basis of light-induced redox regulation in the Calvin-Benson cycle in cyanobacteria
Authors: McFarlane, C
Shah, N
Kabasakal, B
Echeverria, B
Cotton, C
Bubeck, D
Murray, J
Item Type: Journal Article
Abstract: Plants, algae, and cyanobacteria fix carbon dioxide to organic carbon with the Calvin-Benson (CB) cycle. Phosphoribulokinase (PRK) and glyceraldehyde 3 phosphate dehydrogenase (GAPDH) are essential Calvin-Benson cycle enzymes that control substrate availability for the carboxylation enzyme Rubisco. PRK consumes ATP to produce the Rubisco substrate ribulose bisphosphate (RuBP). GAPDH catalyses the reduction step of the CB cycle with NADPH to produce the sugar, glyceraldehyde 3-phosphate (GAP), which is used for regeneration of RuBP and is the main exit point of the cycle. GAPDH and PRK are co-regulated by the redox state of a conditionally disordered protein CP12, which forms a ternary complex with both enzymes. However, the structural basis of Calvin-Benson cycle regulation by CP12 is unknown. Here we show how CP12 modulates the activity of both GAPDH and PRK. Using thermophilic cyanobacterial homologues, we solve crystal structures of GAPDH with different cofactors and CP12 bound, and the ternary GAPDH-CP12-PRK complex by electron cryo-microscopy, we reveal that formation of the N-terminal disulfide pre-orders CP12 prior to binding the PRK active site, which is resolved in complex with CP12. We find that CP12 binding to GAPDH influences substrate accessibility of all GAPDH active sites in the binary and ternary inhibited complexes. Our structural and biochemical data explain how CP12 integrates responses from both redox state and nicotinamide dinucleotide availability to regulate carbon fixation.
Issue Date: 15-Oct-2019
Date of Acceptance: 12-Sep-2019
URI: http://hdl.handle.net/10044/1/73637
DOI: 10.1073/pnas.1906722116
ISSN: 0027-8424
Publisher: National Academy of Sciences
Start Page: 20984
End Page: 20990
Journal / Book Title: Proceedings of the National Academy of Sciences of USA
Volume: 116
Issue: 42
Copyright Statement: © 2019 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND) (https://creativecommons.org/licenses/by-nc-nd/4.0/).
Keywords: Science & Technology
Multidisciplinary Sciences
Science & Technology - Other Topics
redox regulation
carbon fixation
photosynthesis
Calvin-Benson cycle
INTRINSICALLY DISORDERED PROTEIN
CHLAMYDOMONAS-REINHARDTII
GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE
SUPRAMOLECULAR COMPLEX
CP12
PHOSPHORIBULOKINASE
CHLOROPLAST
EXPRESSION
MECHANISM
RESIDUES
Calvin–Benson cycle
carbon fixation
photosynthesis
redox regulation
Bacterial Proteins
Cyanobacteria
Glyceraldehyde 3-Phosphate
Glyceraldehyde-3-Phosphate Dehydrogenases
Light
NADP
Oxidation-Reduction
Phosphotransferases (Alcohol Group Acceptor)
Photosynthesis
Protein Binding
Ribulose-Bisphosphate Carboxylase
Thermosynechococcus
Cyanobacteria
Glyceraldehyde 3-Phosphate
NADP
Ribulose-Bisphosphate Carboxylase
Glyceraldehyde-3-Phosphate Dehydrogenases
Phosphotransferases (Alcohol Group Acceptor)
Bacterial Proteins
Photosynthesis
Protein Binding
Oxidation-Reduction
Light
Publication Status: Published
Online Publication Date: 2019-09-30
Appears in Collections:Faculty of Natural Sciences