A mechanism to prevent production of reactive oxygen species by Escherichia coli respiratory complex I

Abstract

Respiratory complex I plays a central role in cellular energy metabolism coupling NADH oxidation to proton translocation. In humans its dysfunction is associated with degenerative diseases. Here we report the structure of the electron input part of Aquifex aeolicus complex I at up to 1.8 Å resolution with bound substrates in the reduced and oxidized states. The redox states differ by the flip of a peptide bond close to the NADH binding site. The orientation of this peptide bond is determined by the reduction state of the nearby [Fe-S] cluster N1a. Fixation of the peptide bond by site-directed mutagenesis led to an inactivation of electron transfer and a decreased reactive oxygen species (ROS) production. We suggest the redox-gated peptide flip to represent a previously unrecognized molecular switch synchronizing NADH oxidation in response to the redox state of the complex as part of an intramolecular feed-back mechanism to prevent ROS production.

Crystallographic and kinetic analyses of the FdsBG subcomplex of the cytosolic formate dehydrogenase FdsABG from Cupriavidus necator

“…Detailed structural analysis of the reduced and oxidized NuoEF complex from A. aeolicus revealed that the peptide bond between E95 F and S96 F of NuoF undergoes a reversible flip depending on the oxidation state of the protein (20). In the oxidized state, the carbonyl group of E95 F points to the FMN, while in the reduced state it points to the Fe 2 S 2 cluster (Fig.…”

“…For the detailed analysis of the structural differences of FdsBG complex to its homologous subcomplex from NADH dehydrogenase, we used the recently published, high-resolution structure from A. aeolicus, NuoEF complex (20). The NuoE subunit is homologous to the Nqo1 and FdsG subunits, and the NuoF subunit is homologous to the Nqo2 and FdsB subunits ( Fig 3A and 3B).…”

“…The direct and water-mediated interactions between the FMN isoalloxazine ring and the ribityl phosphate tail with FdsB's Rossmann-like fold are conserved in the high-resolution structures of other members of the NADH oxidoreductase family (14,20). (…”

“…In the FdsABG formate dehydrogenase of C. necator, the reducing equivalents from the oxidation of formate pass through a chain of ironsulfur clusters from the molybdenum center in FdsA to the FMN in FdsB, which ultimately reduces NAD + . The FdsBG subcomplex can perform this ultimate step of reducing NAD + , as can the corresponding subcomplexes from both NADH dehydrogenase (15,20,34) and NAD + reducing hydrogenase (35). In our FdsBG structure, the Fe 4 S 4 cluster of FdsB is in close proximity to the C8-methyl of FMN and to highly conserved surface residues that are implicated in the interaction of FdsB with FdsA (i.e., E441 B -S487 B , I451 B -G452 B , and K292 B -L298 B ).…”

Mechanisms of Mitochondrial ROS Production in Assisted Reproduction: The Known, the Unknown, and the Intriguing

“…Upstream bi and tetranuclear iron sulfur clusters can also control superoxide production by limiting FMNH - (i.e., t E RED ) lifetime (i.e., t E RED ). An additional (i.e., bypassed in normal electron tunneling from FMN to the Q binding site) binuclear iron-sulfur cluster termed N1a may also modify superoxide production, potentially by sequestering electrons to decrease [FMNH - ] or via a peptide bond gated switch [ 67 , 68 ]. When electron transfer stalls as occurs in the rotenone (a Q binding site inhibitor) inhibited complex, considerable superoxide production can occur ( Figure 2 ).…”