8HGR

The apo-flavodoxin monomer from Synechococcus elongatus PCC 7942

Summary for 8HGR

• Entry DOI: 10.2210/pdb8hgr/pdb
• Descriptor: Flavodoxin, MAGNESIUM ION, CHLORIDE ION, ... (4 entities in total)
• Functional Keywords: flavodoxin, phosphate binding, redox potential, electron transport, fmn binding
• Biological source: Synechococcus elongatus PCC 7942 = FACHB-805
• Total number of polymer chains: 1
• Total formula weight: 20841.38

Authors

Liu, S.W.,Chen, Y.Y.,Gong, Y.,Cao, P. (deposition date: 2022-11-15, release date: 2022-12-14, Last modification date: 2023-11-29)

Primary citation

Liu, S.,Chen, Y.,Du, T.,Zhao, W.,Liu, X.,Zhang, H.,Yuan, Q.,Gao, L.,Dong, Y.,Gao, X.,Gong, Y.,Cao, P.
A dimer-monomer transition captured by the crystal structures of cyanobacterial apo flavodoxin.
Biochem.Biophys.Res.Commun., 639:134-141, 2022

PubMed Abstract: In cyanobacteria and algae (but not plants), flavodoxin (Fld) replaces ferredoxin (Fd) under stress conditions to transfer electrons from photosystem I (PSI) to ferredoxin-NADP reductase (FNR) during photosynthesis. Fld constitutes a small electron carrier noncovalently bound to flavin mononucleotide (FMN), and also an ideal model for revealing the protein/flavin-binding mechanism because of its relative simplicity compared to other flavoproteins. Here, we report two crystal structures of apo-Fld from Synechococcus sp. PCC 7942, one dimeric structure of 2.09 Å and one monomeric structure of 1.84 Å resolution. Analytical ultracentrifugation showed that in solution, apo-Fld exists both as monomers and dimers. Our dimer structure contains two ligand-binding pockets separated by a distance of 45 Å, much longer than the previous structures of FMN-bound dimers. These results suggested a potential dimer-monomer transition mechanism of cyanobacterial apo-Fld. We further propose that the dimer represents the "standby" state to stabilize itself, while the monomer constitutes the "ready" state to bind FMN. Furthermore, we generated a new docking model of cyanobacterial Fld-FNR complex based on the recently reported cryo-EM structures, and mapped the special interactions between Fld and FNR in detail.

PubMed: 36493556
DOI: 10.1016/j.bbrc.2022.11.089

Experimental method

X-RAY DIFFRACTION (1.84 Å)