Biology subjects

Letts, J. A.

Publications and source records attributed to Letts, J. A..

3 recordsLinked to original sources

bioRxiv2025

In mitochondrial disease respiratory complex III2 assembles complex I via toxic intermediate

Mutations in mitochondrial complex I can cause severe metabolic disease. Although no treatments are available for complex I deficiencies, chronic hypoxia improves lifespan and function in a mouse model of the severe mitochondrial disease Leigh syndrome caused by mutation of complex I subunit NDUFS4. To understand the molecular mechanism of NDUFS4 mutant pathophysiology and hypoxia rescue, we investigated the structure of complex I in respiratory supercomplexes isolated from NDUFS4 mutant mice. We identified complex I assembly intermediates bound to complex III2, proving the cooperative assembly model. Further, an accumulated complex I intermediate is structurally consistent with pathological oxygen-dependent reverse electron transfer, revealing unanticipated pathophysiology and hypoxia rescue mechanisms. Thus, the build-up of toxic intermediates and not simply decreases in complex I levels underlie mitochondrial disease.

biochemistry↗

bioRxiv2022

Resting mitochondrial complex I from Drosophila melanogaster adopts a helix-locked state.

Respiratory complex I is a proton-pumping oxidoreductase key to bioenergetic metabolism. Biochemical studies have found a divide in the behavior of complex I in metazoans that aligns with the evolutionary split between Protostomia and Deuterostomia. Complex I from Deuterostomia including mammals can adopt an off-pathway "deactive" state, whereas complex I from Protostomia cannot. The presence of off-pathway states complicates the interpretation of structural results and has led to considerable mechanistic debate. Here we report the structure of mitochondrial complex I from the thoracic muscles of the model protostomian Drosophila melanogaster. We show that, although D. melanogaster complex I (Dm-CI) does not deactivate the resting state of Dm-CI adopts multiple conformations. We identify a new helix-locked open state in which an N-terminal -helix on the NDUFS4 subunit wedges between the peripheral and membrane arms. Comparison of the Dm-CI structure and conformational states to those observed in bacteria, yeast and mammals provides insight into the roles of subunits across organisms, explains why Dm-CI does not deactivate and reveals incompatibilities with current mechanistic models of complex I turnover. Additionally, the Dm-CI structure and novel regulatory mechanism will allow for the development of more selective pesticides for agriculture and human disease.

biochemistry↗

bioRxiv2020

Atomic structures of respiratory complex III2 , complex IV and supercomplex III2+IV from vascular plants

Mitochondrial complex III (CIII2) and complex IV (CIV), which can associate into a higher-order supercomplex (SC III2+IV), play key roles in respiration. However, structures of these plant complexes remain unknown. We present atomic models of CIII2, CIV and SC III2+IV from Vigna radiata determined by single-particle cryoEM. The structures reveal plant-specific differences in the MPP domain of CIII2 and define the subunit composition of CIV. Conformational heterogeneity analysis of CIII2 revealed long-range, coordinated movements across the complex, as well as the motion of CIII2s iron-sulfur head domain. The CIV structure suggests that, in plants, proton translocation does not occur via the H-channel. The supercomplex interface differs significantly from that in yeast and bacteria in its interacting subunits, angle of approach and limited interactions in the mitochondrial matrix. These structures challenge long-standing assumptions about the plant complexes, generate new mechanistic hypotheses and allow for the generation of more selective agricultural inhibitors.

plant biology↗