4EMI

Toluene dioxygenase reductase in reduced state in complex with NAD+

Summary for 4EMI

• Entry DOI: 10.2210/pdb4emi/pdb
• Related: 3EF6 4EMJ
• Descriptor: TodA, FLAVIN-ADENINE DINUCLEOTIDE, NICOTINAMIDE-ADENINE-DINUCLEOTIDE, ... (4 entities in total)
• Functional Keywords: oxidoreductase, ferredoxin
• Biological source: Pseudomonas putida
• Total number of polymer chains: 1
• Total formula weight: 44432.88

Authors

Lin, T.Y.,Werther, T.,Jeoung, J.H.,Dobbek, H. (deposition date: 2012-04-12, release date: 2012-09-26, Last modification date: 2023-09-13)

Primary citation

Lin, T.Y.,Werther, T.,Jeoung, J.H.,Dobbek, H.
Suppression of Electron Transfer to Dioxygen by Charge Transfer and Electron Transfer Complexes in the FAD-dependent Reductase Component of Toluene Dioxygenase.
J.Biol.Chem., 287:38338-38346, 2012

PubMed Abstract: The three-component toluene dioxygenase system consists of an FAD-containing reductase, a Rieske-type [2Fe-2S] ferredoxin, and a Rieske-type dioxygenase. The task of the FAD-containing reductase is to shuttle electrons from NADH to the ferredoxin, a reaction the enzyme has to catalyze in the presence of dioxygen. We investigated the kinetics of the reductase in the reductive and oxidative half-reaction and detected a stable charge transfer complex between the reduced reductase and NAD(+) at the end of the reductive half-reaction, which is substantially less reactive toward dioxygen than the reduced reductase in the absence of NAD(+). A plausible reason for the low reactivity toward dioxygen is revealed by the crystal structure of the complex between NAD(+) and reduced reductase, which shows that the nicotinamide ring and the protein matrix shield the reactive C4a position of the isoalloxazine ring and force the tricycle into an atypical planar conformation, both factors disfavoring the reaction of the reduced flavin with dioxygen. A rapid electron transfer from the charge transfer complex to electron acceptors further reduces the risk of unwanted side reactions, and the crystal structure of a complex between the reductase and its cognate ferredoxin shows a short distance between the electron-donating and -accepting cofactors. Attraction between the two proteins is likely mediated by opposite charges at one large patch of the complex interface. The stability, specificity, and reactivity of the observed charge transfer and electron transfer complexes are thought to prevent the reaction of reductase(TOL) with dioxygen and thus present a solution toward conflicting requirements.

PubMed: 22992736
DOI: 10.1074/jbc.M112.374918

Experimental method

X-RAY DIFFRACTION (1.806 Å)