bims-cytox1 2021-05-16 papers

bims-cytox1

Biomed News

on Cytochrome oxidase subunit 1

Issue of 2021–05–16
seven papers selected by
Gavin McStay, Staffordshire University

Mitochondrial matrix proteases - quality control and beyond.
NMR structural analysis of the yeast cytochrome c oxidase subunit Cox13 and its interaction with ATP.
Architecture and assembly dynamics of the essential mitochondrial chaperone complex TIM9·10·12.
Mitochondrial CHCHD2: Disease-Associated Mutations, Physiological Functions, and Current Animal Models.
Erv1 and cytochrome c mediate rapid electron transfer via a collision-type interaction.
Physiological concentrations of cyanide stimulate mitochondrial Complex IV and enhance cellular bioenergetics.
Quantification of Local Electric Field Changes at the Active Site of Cytochrome c Oxidase by Fourier Transform Infrared Spectroelectrochemical Titrations.

FEBS J. 2021 May 10.

Mitochondrial matrix proteases - quality control and beyond.

Karolina Szczepanowska, Aleksandra Trifunovic.

  To ensure correct function, mitochondria have developed several mechanisms of protein quality control (QC). Protein homeostasis highly relies on chaperones and proteases to maintain proper folding and remove damaged proteins that might otherwise form cell-toxic aggregates. Besides quality control, mitochondrial proteases modulate and regulate many essential functions, such as trafficking, processing, and activation of mitochondrial proteins, mitochondrial dynamics, mitophagy, and apoptosis. Therefore, the impaired function of mitochondrial proteases is associated with various pathological conditions, including cancer, metabolic syndromes, and neurodegenerative disorders. This review recapitulates and discusses the emerging roles of two major proteases of the mitochondrial matrix, LON and ClpXP. Although commonly acknowledge for their protein quality control role, recent advances have uncovered several highly regulated processes controlled by the LON and ClpXP connected to mitochondrial gene expression and respiratory chain function maintenance. Furthermore, both proteases have been lately recognized as potent targets for anti-cancer therapies, and we summarize those findings.

Keywords:  ClpXP; LONP1; cancer; degradation; metabolism; mitochondria; mitochondrial matrix; mtDNA; proteases; protein quality control; proteolysis; respiratory complexes

DOI:  https://doi.org/10.1111/febs.15964
BMC Biol. 2021 May 10. 19(1): 98

NMR structural analysis of the yeast cytochrome c oxidase subunit Cox13 and its interaction with ATP.

Shu Zhou, Pontus Pettersson, Markus L Björck, Hannah Dawitz, Peter Brzezinski, Lena Mäler, Pia Ädelroth.

   BACKGROUND: Mitochondrial respiration is organized in a series of enzyme complexes in turn forming dynamic supercomplexes. In Saccharomyces cerevisiae (baker's yeast), Cox13 (CoxVIa in mammals) is a conserved peripheral subunit of Complex IV (cytochrome c oxidase, CytcO), localized at the interface of dimeric bovine CytcO, which has been implicated in the regulation of the complex.
RESULTS: Here, we report the solution NMR structure of Cox13, which forms a dimer in detergent micelles. Each Cox13 monomer has three short helices (SH), corresponding to disordered regions in X-ray or cryo-EM structures of homologous proteins. Dimer formation is mainly induced by hydrophobic interactions between the transmembrane (TM) helix of each monomer. Furthermore, an analysis of chemical shift changes upon addition of ATP revealed that ATP binds at a conserved region of the C terminus with considerable conformational flexibility.
CONCLUSIONS: Together with functional analysis of purified CytcO, we suggest that this ATP interaction is inhibitory of catalytic activity. Our results shed light on the structural flexibility of an important subunit of yeast CytcO and provide structure-based insight into how ATP could regulate mitochondrial respiration.

Keywords:  ATP; Membrane protein; NMR; Solution structure

DOI:  https://doi.org/10.1186/s12915-021-01036-x
Structure. 2021 May 03. pii: S0969-2126(21)00125-8. [Epub ahead of print]

Architecture and assembly dynamics of the essential mitochondrial chaperone complex TIM9·10·12.

Katharina Weinhäupl, Yong Wang, Audrey Hessel, Martha Brennich, Kresten Lindorff-Larsen, Paul Schanda.

  Tim chaperones transport membrane proteins to the two mitochondrial membranes. TIM9·10, a 70 kDa protein complex formed by 3 copies of Tim9 and Tim10, guides its clients across the aqueous compartment. The TIM9·10·12 complex is the anchor point at the inner-membrane insertase TIM22. The subunit composition of TIM9·10·12 remains debated. Joint NMR, small-angle X-ray scattering, and MD simulation data allow us to derive a structural model of the TIM9·10·12 assembly, with a 2:3:1 stoichiometry (Tim9:Tim10:Tim12). Both TIM9·10 and TIM9·10·12 hexamers are in a dynamic equilibrium with their constituent subunits, exchanging on a minutes timescale. NMR data establish that the subunits exhibit large conformational dynamics: when the conserved cysteines of the CX3C-Xn-CX3C motifs are formed, short α helices are formed, and these are fully stabilized only upon formation of the mature hexameric chaperone. We propose that the continuous subunit exchange allows mitochondria to control their level of inter-membrane space chaperones.

Keywords:  NMR spectroscopy; TIM9·10; TIM9·10·12; kinetics; mitochondrial biogenesis; molecular dynamics simulations; protein import; real-time NMR; small-angle X-ray scattering; subunit exchange

DOI:  https://doi.org/10.1016/j.str.2021.04.009
Front Aging Neurosci. 2021 ;13 660843

Mitochondrial CHCHD2: Disease-Associated Mutations, Physiological Functions, and Current Animal Models.

Teresa R Kee, Pamela Espinoza Gonzalez, Jessica L Wehinger, Mohammed Zaheen Bukhari, Aizara Ermekbaeva, Apoorva Sista, Peter Kotsiviras, Tian Liu, David E Kang, Jung-A A Woo.

  Rare mutations in the mitochondrial protein coiled-coil-helix-coiled-coil-helix domain containing 2 (CHCHD2) are associated with Parkinson's disease (PD) and other Lewy body disorders. CHCHD2 is a bi-organellar mediator of oxidative phosphorylation, playing crucial roles in regulating electron flow in the mitochondrial electron transport chain and acting as a nuclear transcription factor for a cytochrome c oxidase subunit (COX4I2) and itself in response to hypoxic stress. CHCHD2 also regulates cell migration and differentiation, mitochondrial cristae structure, and apoptosis. In this review, we summarize the known disease-associated mutations of CHCHD2 in Asian and Caucasian populations, the physiological functions of CHCHD2, how CHCHD2 mutations contribute to α-synuclein pathology, and current animal models of CHCHD2. Further, we discuss the necessity of continued investigation into the divergent functions of CHCHD2 and CHCHD10 to determine how mutations in these similar mitochondrial proteins contribute to different neurodegenerative diseases.

Keywords:  CHCHD10; CHCHD2; Lewy body disorders; Parkinson’s disease; mitochondria

DOI:  https://doi.org/10.3389/fnagi.2021.660843
J Mol Biol. 2021 May 07. pii: S0022-2836(21)00263-1. [Epub ahead of print] 167045

Erv1 and cytochrome c mediate rapid electron transfer via a collision-type interaction.

Esra Peker, Alican J Erdogan, Alexander N Volkov, Jan Riemer.

  Being essential for oxidative protein folding in the mitochondrial intermembrane space, the mitochondrial disulfide relay relies on the electron transfer (ET) from the sulfhydryl oxidase Erv1 to cytochrome c (Cc). Using solution NMR spectroscopy, we demonstrate that while the yeast Cc-Erv1 system is functionally active, no observable binding of the protein partners takes place. The transient interaction between Erv1 and Cc can be rationalized by molecular modeling, suggesting that a large surface area of Erv1 can sustain a fast ET to Cc via a collision-type mechanism, without the need for a canonical protein complex formation. We suggest that, by preventing the direct ET to molecular oxygen (O2), the collision-type Cc-Erv1 interaction plays a role in protecting the organism against reactive oxygen species.

Keywords:  Erv1; cytochrome c; disulfide relay; electron transfer; transient protein complex

DOI:  https://doi.org/10.1016/j.jmb.2021.167045
Proc Natl Acad Sci U S A. 2021 May 18. pii: e2026245118. [Epub ahead of print]118(20):

Physiological concentrations of cyanide stimulate mitochondrial Complex IV and enhance cellular bioenergetics.

Elisa B Randi, Karim Zuhra, Laszlo Pecze, Theodora Panagaki, Csaba Szabo.

  In mammalian cells, cyanide is viewed as a cytotoxic agent, which exerts its effects through inhibition of mitochondrial Complex IV (Cytochrome C oxidase [CCOx]). However, the current report demonstrates that cyanide's effect on CCOx is biphasic; low (nanomolar to low-micromolar) concentrations stimulate CCOx activity, while higher (high-micromolar) concentrations produce the "classic" inhibitory effect. Low concentrations of cyanide stimulated mitochondrial electron transport and elevated intracellular adenosine triphosphate (ATP), resulting in the stimulation of cell proliferation. The stimulatory effect of cyanide on CCOx was associated with the removal of the constitutive, inhibitory glutathionylation on its catalytic 30- and 57-kDa subunits. Transfer of diluted Pseudomonas aeruginosa (a cyanide-producing bacterium) supernatants to mammalian cells stimulated cellular bioenergetics, while concentrated supernatants were inhibitory. These effects were absent with supernatants from mutant Pseudomonas lacking its cyanide-producing enzyme. These results raise the possibility that cyanide at low, endogenous levels serves regulatory purposes in mammals. Indeed, the expression of six putative mammalian cyanide-producing and/or -metabolizing enzymes was confirmed in HepG2 cells; one of them (myeloperoxidase) showed a biphasic regulation after cyanide exposure. Cyanide shares features with "classical" mammalian gasotransmitters NO, CO, and H2S and may be considered the fourth mammalian gasotransmitter.

Keywords:  bioenergetics; gasotransmitters; mitochondria

DOI:  https://doi.org/10.1073/pnas.2026245118
Front Chem. 2021 ;9 669452

Quantification of Local Electric Field Changes at the Active Site of Cytochrome c Oxidase by Fourier Transform Infrared Spectroelectrochemical Titrations.

Federico Baserga, Jovan Dragelj, Jacek Kozuch, Hendrik Mohrmann, Ernst-Walter Knapp, Sven T Stripp, Joachim Heberle.

  Cytochrome c oxidase (CcO) is a transmembrane protein complex that reduces molecular oxygen to water while translocating protons across the mitochondrial membrane. Changes in the redox states of its cofactors trigger both O2 reduction and vectorial proton transfer, which includes a proton-loading site, yet unidentified. In this work, we exploited carbon monoxide (CO) as a vibrational Stark effect (VSE) probe at the binuclear center of CcO from Rhodobacter sphaeroides. The CO stretching frequency was monitored as a function of the electrical potential, using Fourier transform infrared (FTIR) absorption spectroelectrochemistry. We observed three different redox states (R4CO, R2CO, and O), determined their midpoint potential, and compared the resulting electric field to electrostatic calculations. A change in the local electric field strength of +2.9 MV/cm was derived, which was induced by the redox transition from R4CO to R2CO. We performed potential jump experiments to accumulate the R2CO and R4CO species and studied the FTIR difference spectra in the protein fingerprint region. The comparison of the experimental and computational results reveals that the key glutamic acid residue E286 is protonated in the observed states, and that its hydrogen-bonding environment is disturbed upon the redox transition of heme a3. Our experiments also suggest propionate A of heme a3 changing its protonation state in concert with the redox state of a second cofactor, heme a. This supports the role of propionic acid side chains as part of the proton-loading site.

Keywords:  carbon monoxide; electron transfer; electrostatic potential; infrared spectroscopy; proton transfer; redox chemistry; vibrational Stark effect

DOI:  https://doi.org/10.3389/fchem.2021.669452