bims-cytox1 2025-03-23 papers

Proc Natl Acad Sci U S A. 2025 Mar 25. 122(12): e2416162122

A splendid molecular factory: De- and reconstruction of the mammalian respiratory chain.

Lukas Rimle, Ben P Phillips, Isabela M Codo Costa Barra, Noëlle Arnold, Charlie Hennebert, Thomas Meier, Christoph von Ballmoos.

Mitochondrial respiratory complexes I to IV and the F1Fo-ATP synthase (complex V) are large protein assemblies producing the universal cellular energy currency adenosine triphosphate (ATP). Individual complexes have been extensively studied in vitro, but functional co-reconstitution of several mammalian complexes into proteoliposomes, in particular, the combination of a primary pump with the ATP synthase, is less well understood. Here, we present a generic and scalable strategy to purify mammalian respiratory complexes I, III and the ATP synthase from enriched mitochondria in enzymatically fully active form, and procedures to reassemble the complexes into liposomes. A robust functionality can be shown by in situ monitoring of ATP synthesis rates and by using selected inhibitors of the respiratory chain complexes. By inclusion of cytochrome c oxidase, our procedures allowed us to reconstruct the entire mitochondrial respiratory chain (complexes I, III, IV, and V) in ubiquinone Q10 containing liposomes, demonstrating oxidative phosphorylation by nicotinamide adenine dinucleotide hydrogen driven ATP synthesis. The system was fully coupled at all levels and was used to probe cardiolipin as an essential component to activate the mammalian respiratory chain. Structural characterization using electron cryomicroscopy allowed us to resolve apo-state complex III and complex V at high and medium resolution, respectively, using in silico particle sorting, confirming the presence of all protein subunits and cofactors in native stoichiometry and conformation. The reported findings will facilitate future endeavors to characterize or modulate these key bioenergetic processes.

Keywords: artificial ATP production; cryo-EM; mitochondria; oxidative phosphorylation; respiratory chain

DOI: https://doi.org/10.1073/pnas.2416162122

Science. 2025 Mar 21. 387(6740): 1296-1301

In-cell architecture of the mitochondrial respiratory chain.

Florent Waltz, Ricardo D Righetto, Lorenz Lamm, Thalia Salinas-Giegé, Ron Kelley, Xianjun Zhang, Martin Obr, Sagar Khavnekar, Abhay Kotecha, Benjamin D Engel.

Mitochondria regenerate adenosine triphosphate (ATP) through oxidative phosphorylation. This process is carried out by five membrane-bound complexes collectively known as the respiratory chain, working in concert to transfer electrons and pump protons. The precise organization of these complexes in native cells is debated. We used in situ cryo-electron tomography to visualize the native structures and organization of several major mitochondrial complexes in Chlamydomonas reinhardtii cells. ATP synthases and respiratory complexes segregate into curved and flat crista membrane domains, respectively. Respiratory complexes I, III, and IV assemble into a respirasome supercomplex, from which we determined a native 5-angstrom (Å) resolution structure showing binding of electron carrier cytochrome c. Combined with single-particle cryo-electron microscopy at 2.4-Å resolution, we model how the respiratory complexes organize inside native mitochondria.

DOI: https://doi.org/10.1126/science.ads8738

Epilepsia Open. 2025 Mar 17.

Compound heterozygosity of a De novo 16q24.1 deletion and missense mutation in COX4I1 leads to developmental regression, intellectual disability, and seizures.

Zhen Liu, Mei He, Xuan Luo, Hu Pan, Xiao Mao, Jinping Su.

The COX4I1 is responsible for encoding a crucial component of cytochrome c oxidase, integral to electron transport in the mitochondrial respiratory chain. Mutations in COX4I1 can result in a rare autosomal recessive disorder characterized by growth retardation, slow weight gain, microcephaly, and potentially, hematologic symptoms such as Fanconi anemia or neurological impairments including developmental regression and severe epilepsy. In this study, we report the first case of COX4I1 deficiency in China, identified in a 6-year-old boy. The patient exhibited developmental regression, epilepsy, low body weight, microcephaly, generalized muscle hypotonia, and progressive cerebral atrophy, but without hematologic damage or short stature. Compound heterozygosity for a de novo 16q24.1 deletion and a P152T missense mutation in the COX4I1 was detected. The P152T missense mutation is previously reported in patients with similar clinical manifestations. Additionally, we provide the first instance of progressive brain atrophy observed through MRI in a COX4I1 deficiency patient, broadening our understanding of the mutation spectrum and clinical phenotype of this genetic disorder. PLAIN LANGUAGE SUMMARY: We discovered the first case of COX4I1 deficiency in China, identified in a 6-year-old boy. The patient exhibited developmental regression, epilepsy, low body weight, microcephaly, generalized muscle hypotonia, and progressive cerebral atrophy, but without hematologic damage or short stature. Compound heterozygosity for a de novo 16q24.1 deletion and a P152T missense mutation in the COX4I1 was detected. Additionally, we provide the first instance of progressive brain atrophy observed through MRI in a COX4I1 deficiency patient, broadening our understanding of the mutation spectrum and clinical phenotype of this genetic disorder.

Keywords: COX4I1; cytochrome c oxidase; developmental regression; epilepsy; intellectual disability; progressive cerebral atrophy

DOI: https://doi.org/10.1002/epi4.13117

J Exp Biol. 2025 Mar 18. pii: jeb.249613. [Epub ahead of print]

Dietary modification of membrane composition mimics characteristics of thermal acclimation in the Eastern newt (Notophthalmus viridescens).

Patrick M Mineo, Cameron J World, T A Morris, Nancy J Berner.

Acclimation in response to seasonal temperature fluctuations is well described across animal taxa. Our previous studies on adult Eastern red spotted newts have demonstrated that winter or cold-acclimated newts prefer lower cloacal temperatures, have higher standard metabolic rates (SMR), exhibit higher skeletal muscle cytochrome C oxidase (CCO) and citrate synthase (CS) activity, and possess membranes composed of elevated polyunsaturated fatty acid (PUFA) content compared to skeletal muscle of summer or warm-acclimated newts. Acclimation to cold also results in partial compensation of locomotor performance. Additionally, northern populations have higher CS and CCO activity and a higher degree of membrane unsaturation compared to southern populations regardless of acclimation conditions. In the present study we tested the hypothesis that modification of membrane FA composition mimics characteristics of thermal acclimation. We modified membrane composition in newts independent of environmental temperature by feeding them diets differing in FA composition (saturated, monounsaturated, and n3 or n6 PUFA diets) and measured CCO and CS activity, SMR, preferred cloacal temperature, locomotor performance and thermal tolerance. Here we present data suggesting that a diet-mediate elevation of PUFA in tissue membranes results in lower proffered body temperature, increased metabolic rate, increased burst speed at low temperature, and decreased burst speed at high temperature. This introduces an ectothermic vertebrate model system that acclimates characteristics across levels of biological organization in which we can effectively uncouple membrane composition from environmental temperature or light cycle, and further suggests that diet may be an important component of thermal acclimation in nature.

Keywords: Acclimation; Membrane; Metabolism; Thermal

DOI: https://doi.org/10.1242/jeb.249613