5DQR

The crystal structure of Arabidopsis 7-hydroxymethyl chlorophyll a reductase (HCAR)

Summary for 5DQR

• Entry DOI: 10.2210/pdb5dqr/pdb
• Descriptor: 7-hydroxymethyl chlorophyll a reductase, chloroplastic, IRON/SULFUR CLUSTER, FLAVIN-ADENINE DINUCLEOTIDE, ... (4 entities in total)
• Functional Keywords: iron-sulfur flavoenzyme, hcar, chlorophyll cycle, oxidoreductase
• Biological source: Arabidopsis thaliana (Mouse-ear cress)
• Cellular location: Plastid, chloroplast : Q8GS60
• Total number of polymer chains: 6
• Total formula weight: 303342.41

Authors

Wang, X.,Liu, L. (deposition date: 2015-09-15, release date: 2016-04-20, Last modification date: 2024-03-20)

Primary citation

Wang, X.,Liu, L.
Crystal Structure and Catalytic Mechanism of 7-Hydroxymethyl Chlorophyll a Reductase
J.Biol.Chem., 291:13349-13359, 2016

PubMed Abstract: 7-Hydroxymethyl chlorophyll a reductase (HCAR) catalyzes the second half-reaction in chlorophyll b to chlorophyll a conversion. HCAR is required for the degradation of light-harvesting complexes and is necessary for efficient photosynthesis by balancing the chlorophyll a/b ratio. Reduction of the hydroxymethyl group uses redox cofactors [4Fe-4S] cluster and FAD to transfer electrons and is difficult because of the strong carbon-oxygen bond. Here, we report the crystal structure of Arabidopsis HCAR at 2.7-Å resolution and reveal that two [4Fe-4S]clusters and one FAD within a very short distance form a consecutive electron pathway to the substrate pocket. In vitro kinetic analysis confirms the ferredoxin-dependent electron transport chain, thus supporting a proton-activated electron transfer mechanism. HCAR resembles a partial reconstruction of an archaeal F420-reducing [NiFe] hydrogenase, which suggests a common mode of efficient proton-coupled electron transfer through conserved cofactor arrangements. Furthermore, the trimeric form of HCAR provides a biological clue of its interaction with light-harvesting complex II.

PubMed: 27072131
DOI: 10.1074/jbc.M116.720342

Experimental method

X-RAY DIFFRACTION (2.7 Å)