Oral Presentation The 46th Lorne Conference on Protein Structure and Function 2021

Structural and functional characterisation of mitochondrial complex IV assembly factors (#7)

Shadi Maghool 1 , Luke Formosa 2 , David Stroud 3 , David Aragao 4 , Mike Ryan 2 , Megan Maher 1
  1. School of Chemistry , The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, VIC, Australia
  2. Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
  3. Department of Biochemistry and Molecular Biology , The Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne., Melbourne, VIC, Australia
  4. Diamond Light Source, Harwell Science and Innovation Campus, Didcot, UK

The mitochondrial oxidative phosphorylation system generates the bulk of cellular ATP, fuelling the energy demands of most eukaryotes. ComplexIV (COX), a multi-subunit oxidoreductase, is the terminal complex of the mitochondrial electron transport chain. Assembly of COX requires the participation of a host of cysteine-rich proteins of the mitochondrial intermembrane space, which take part in a tightly choreographed series of intermolecular interactions for COX assembly. In addition, COX requires the incorporation of copper ions and heme cofactors for the activity of the complex. Crucially, disruptions in this pathway lead to defects in COX assembly and, in humans, manifests in mitochondrial disease [1].

Despite the importance of COX assembly in health and mitochondrial disease, we have only a limited understanding of the molecular basis of its biogenesis, due to a lack of knowledge about structures and precise functions of the individual assembly factors. This presentation will describe the role of COA6 and COA7 proteins in COX biogenesis using structural and functional approaches and importantly, explain the molecular mechanisms of pathogeneses that occur as a result of identified patient mutations. Assembly of the COX2-CuA site requires the action of assembly factors that facilitate both thiol-oxidoreductase and copper trafficking processes. COA6 binds copper with femtomolar affinity and has been proposed to play a role in the biogenesis of the CuA site [2,3]. Equally, the measured redox potential of the Cys disulfide in COA6 indicates COA6 would be capable of catalysing the reduction of disulfide bonds within assembly factor proteins and COX2, which is a well-recognised requirement for copper transfer [3,4]. Intriguingly, characterisation of recombinant COA7 shows that the protein is capable of binding heme with micromolar affinity. These findings point to potential defects in heme incorporation, required for the stability of the COX2 module as being a contributor to defects in COX biogenesis.

 

  1. [1] Timon-Gomez, A., Nyvltova, E., Abriata, L. A., Vila, A. J., Hosler, J., and Barrientos, A. (2018) Mitochondrial cytochrome c oxidase biogenesis: Recent developments, Seminars in cell & developmental biology 76, 163-178.
  2. [2] Stroud, D. A., Maher, M. J., Lindau, C., Vögtle, F. N., Frazier, A. E., Surgenor, E., … Ryan, M. T. (2015). COA6 is a mitochondrial complex IV assembly factor critical for biogenesis of mtDNA-encoded COX2. Human molecular genetics, 24(19), 5404–5415. doi:10.1093/hmg/ddv265
  3. [3] Maghool, S., Cooray, N., Stroud, D. A., Aragão, D., Ryan, M. T., & Maher, M. J. (2019). Structural and functional characterization of the mitochondrial complex IV assembly factor Coa6. Life science alliance, 2(5), e201900458. doi:10.26508/lsa.2019004583.
  4. [4] Maghool, S., Ryan, M. T., & Maher, M. J. (2020). What Role Does COA6 Play in Cytochrome C Oxidase Biogenesis: A Metallochaperone or Thiol Oxidoreductase, or Both?. International journal of molecular sciences, 21(19), E6983.