7qh2 | pdb_00007qh2
Cryo-EM structure of Ldh-EtfAB complex from Acetobacterium woodii
Structural highlights
Function[LCTC_ACEWD] The lactate dehydrogenase-Etf complex catalyzes the oxidation of lactate to pyruvate. It uses flavin-based electron confurcation to drive endergonic lactate oxidation with NAD(+) as oxidant at the expense of simultaneous exergonic electron flow from reduced ferredoxin to NAD(+). The electron transfer flavoprotein (Etf) mediates the electron transfer between the different donors and acceptors.[1] [LCTD_ACEWD] The lactate dehydrogenase-Etf complex catalyzes the oxidation of lactate to pyruvate. It uses flavin-based electron confurcation to drive endergonic lactate oxidation with NAD(+) as oxidant at the expense of simultaneous exergonic electron flow from reduced ferredoxin to NAD(+).[2] [LCTB_ACEWD] The lactate dehydrogenase-Etf complex catalyzes the oxidation of lactate to pyruvate. It uses flavin-based electron confurcation to drive endergonic lactate oxidation with NAD(+) as oxidant at the expense of simultaneous exergonic electron flow from reduced ferredoxin to NAD(+). The electron transfer flavoprotein (Etf) mediates the electron transfer between the different donors and acceptors.[3] Publication Abstract from PubMedLactate oxidation with NAD(+) as electron acceptor is a highly endergonic reaction. Some anaerobic bacteria overcome the energetic hurdle by flavin-based electron bifurcation/confurcation (FBEB/FBEC) using a lactate dehydrogenase (Ldh) in concert with the electron-transferring proteins EtfA and EtfB. The electron cryo-microscopically characterized (Ldh-EtfAB)2 complex of Acetobacterium woodii at 2.43 A resolution consists of a mobile EtfAB shuttle domain located between the rigid central Ldh and the peripheral EtfAB base units. The FADs of Ldh and the EtfAB shuttle domain contact each other thereby forming the D (dehydrogenation-connected) state. The intermediary Glu37 and Glu139 may harmonize the redox potentials between the FADs and the pyruvate/lactate pair crucial for FBEC. By integrating Alphafold2 calculations a plausible novel B (bifurcation-connected) state was obtained allowing electron transfer between the EtfAB base and shuttle FADs. Kinetic analysis of enzyme variants suggests a correlation between NAD(+) binding site and D-to-B-state transition implicating a 75 degrees rotation of the EtfAB shuttle domain. The FBEC inactivity when truncating the ferredoxin domain of EtfA substantiates its role as redox relay. Lactate oxidation in Ldh is assisted by the catalytic base His423 and a metal center. On this basis, a comprehensive catalytic mechanism of the FBEC process was proposed. Structure-based electron-confurcation mechanism of the Ldh-EtfAB complex.,Kayastha K, Katsyv A, Himmrich C, Welsch S, Schuller JM, Ermler U, Muller V Elife. 2022 Jun 24;11. pii: 77095. doi: 10.7554/eLife.77095. PMID:35748623[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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