A vital characteristic of living systems is their ability to produce biological energy (ATP) efficiently. ATP is essential for cellular functions including biosynthesis, transport, signal transduction, chemo- and photo- taxis and thermogenesis. Energy producing complexes are widespread among organisms, and their improper function leads to devastating health problems and human diseases as well as low crop yields in plants. The long-term goal of this project is to understand the structure, mechanism of function and biogenesis of cytochrome (cyt) components of energy transduction pathways. These are important enzymes whose absence, or malfunction are the causes of multiple human diseases, including many muscular and neurological disorders. For these studies, prokaryotes provide simpler model systems that are evolutionarily conserved and closely related to eukaryotic organelles. This project uses molecular genetics, biochemical and biophysical approaches, with a sharp focus on the structure and function of the cyt bc1 or Complex III.
The specific aims of this proposal include 1- the molecular basis of oxygen tolerance of the quinol oxidation site of the cyt bc1 to address how this aerobic enzyme avoids the production of unwanted reactive oxygen species in the presence of oxygen, 2- exploration of the Zn binding residues of cyt b at the Qo site to probe their involvement in H+ conduction, and 3- development and characterization of heterodimer cyt bc1 variants to address intra- and inter-monomer structural and functional communications and regulations within the cyt bc1, to probe the links between the dimeric architecture and the mechanism of function of this enzyme. These studies are expected to greatly enhance our understanding and knowledge of energy transduction enzymes. Information gained using the simpler bacterial system could be generally applicable to the structurally more complex but functionally similar and evolutionarily related organelle-derived enzyme, and could provide invaluable information for elucidating the molecular bases and diagnoses of mitochondrial and other human diseases, including neuropathies, myopathies and aging.

Public Health Relevance

This research aims to define the structure-function and biogenesis of energy transduction enzymes. These proteins are the major sources of reactive oxygen species that are extremely harmful for human cells, and their biogenesis components form the molecular bases of many common mitochondrial diseases in humans. Malfunction of these enzymes induce multiple human illnesses, extending from maternally inherited mitochondrial diseases to neuromuscular degenerative disorders, as well as cancer and aging.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Macromolecular Structure and Function A Study Section (MSFA)
Program Officer
Anderson, Vernon
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Pennsylvania
Schools of Arts and Sciences
United States
Zip Code
Khalfaoui-Hassani, Bahia; Wu, Hongjiang; Blaby-Haas, Crysten E et al. (2018) Widespread Distribution and Functional Specificity of the Copper Importer CcoA: Distinct Cu Uptake Routes for Bacterial Cytochrome c Oxidases. MBio 9:
Trasnea, Petru-Iulian; Andrei, Andreea; Marckmann, Dorian et al. (2018) A Copper Relay System Involving Two Periplasmic Chaperones Drives cbb3-Type Cytochrome c Oxidase Biogenesis in Rhodobacter capsulatus. ACS Chem Biol 13:1388-1397
Sandri, Federica; Musiani, Francesco; Selamoglu, Nur et al. (2018) Pseudomonas pseudoalcaligenes KF707 grown with biphenyl expresses a cytochrome caa3 oxidase that uses cytochrome c4 as electron donor. FEBS Lett 592:901-915
Tropeano, Concetta Valentina; Fiori, Jessica; Carelli, Valerio et al. (2018) Complex II phosphorylation is triggered by unbalanced redox homeostasis in cells lacking complex III. Biochim Biophys Acta Bioenerg 1859:182-190
Vos, Marten H; Reeder, Brandon J; Daldal, Fevzi et al. (2017) Correction: Ultrafast photochemistry of the bc1 complex. Phys Chem Chem Phys 19:9320
Foley, Shawn W; Gosai, Sager J; Wang, Dongxue et al. (2017) A Global View of RNA-Protein Interactions Identifies Post-transcriptional Regulators of Root Hair Cell Fate. Dev Cell 41:204-220.e5
Vos, Marten H; Reeder, Brandon J; Daldal, Fevzi et al. (2017) Ultrafast photochemistry of the bc1complex. Phys Chem Chem Phys 19:6807-6813
Onder, Ozlem; Verissimo, Andreia F; Khalfaoui-Hassani, Bahia et al. (2017) Absence of Thiol-Disulfide Oxidoreductase DsbA Impairs cbb3-Type Cytochrome c Oxidase Biogenesis in Rhodobacter capsulatus. Front Microbiol 8:2576
Verissimo, Andreia F; Khalfaoui-Hassani, Bahia; Hwang, Josephine et al. (2017) The thioreduction component CcmG confers efficiency and the heme ligation component CcmH ensures stereo-specificity during cytochrome c maturation. J Biol Chem 292:13154-13167
Trasnea, Petru-Iulian; Utz, Marcel; Khalfaoui-Hassani, Bahia et al. (2016) Cooperation between two periplasmic copper chaperones is required for full activity of the cbb3 -type cytochrome c oxidase and copper homeostasis in Rhodobacter capsulatus. Mol Microbiol 100:345-61

Showing the most recent 10 out of 54 publications