The crux of energy transduction in most organisms is the electron transport chain. Here, electrons that have been stripped from nutrients flow down a series of membrane-bound complexes to electron acceptors such as oxygen. The liberated redox energy is used to translocate proton across a membrane, building a proton motive force that is used to drive other reactions away from equilibrium, the most important of which is the phosphorylation of ADP to ATP. The ATP is then used to power diverse reactions in the cell.
We understand the electron transport of a few model systems increasingly well, but there is a great deal of diversity in electron transport chains of both pathogenic and nonpathogenic species that is not captured in these model species. An excellent example of this is the electron transport chain of the mycobacteria group, which include the causative agents of tuberculosis and leprosy. Many of the complexes of the pathogens are highly divergent from their better characterised relatives, and there remains a huge amount to discover and learn. In addition to being of fundamental interest, these systems are a validated drug target: the approved drug bedaquiline targets ATP synthase and Q203, which has entered phase-2 clinical trials, targets the bcc1 complex. We are working to understand these unique complexes on both structural and functional levels, using cryoEM, enzyme kinetics, and haem spectroscopy, and also to relate these biophysical data to the physiology of the organism using microbiology and molecular biology.
There has been an explosion of high quality cryoEM structures- some at incredible resolutions. However, just as crystallisation is essential for X-ray crystallographic studies, the generation of good cryo-grids underpins any cryoEM project. This is true for all targets, but is particularly critical for some of the targets that are most interesting: delicate membrane proteins and intricate assemblies. Cryo-grids are prepared by plunge freezing very thin water films into a cryogen like liquid ethane, forming thin sheets of vitreous ice that can then be loaded into electron microscopes. Previous experience has shown that in addition to the presence of a very large air-water interface, the structure of the substrate of the grid is also critical, for example hydrophilic surfaces are significantly kinder to the protein than carbon. We are hoping to extend these observations with further improved surfaces, using compounds such as sugar dendrimers. These surfaces should be superior for isolated macromolecules but also may allow adherent cells to be grown on the surfaces in a more physiological environment.
Jamie studied at the University of Leeds and the National University of Singapore for his undergraduate degree in Microbiology. Working for Mike Webb for two summers, he became interested in the ‘chemical’ side of biochemistry and so pursued a PhD at the MRC Mitochondrial Biology Unit at the University of Cambridge with Judy Hirst, developing methods to measure proton and electron transfer reactions in the mammalian mitochondrial electron transport chain. Following his PhD, he stayed on with Judy as a MRC Career Development Fellow, to learn cryo-electron microscopy (cryoEM) from Vinothkumar Kutti Ragunath (then at the MRC LMB, now NCBS, India), pushing the resolution of the mitochondrial complex I cryoEM maps, allowing the visualisation of key structural features and providing information on the physiological regulation of this crucial complex. After a brief stay in Ben Luisi’s laboratory in the Cambridge Biochemistry Department looking at bacterial antibiotic transporters and ribonucleoprotein assemblies, he came to the University of York to establish his own group and cryoEM as a technique in the YSBL.
Interested Masters and PhD students are encouraged to contact Jamie for further information about available projects. As our work sits at the interface of biology and chemistry/physics people from either scientific background are encouraged to get in touch.
Agip AA*, Blaza JN*, Bridges HR, Viscomi C, Rawson S, Muench SP, Hirst J. CryoEM structures of complex I from mouse heart mitochondria in two biochemically-defined states. Nature Structural and Molecular Biology 25, 2018.
Blaza JN, Vinothkumar KR, Hirst J. Structure of mammalian respiratory complex I in the deactive state. Structure 26, 2018.
Milenkovic D*, Blaza JN*, Larrson N-G, Hirst J. The enigma of the respiratory chain supercomplex. Cell Metabolism 25, 2017.
Blaza JN*, Bridges HR*, Aragão D, Dunn EA, Heikal A, Cook GM, Nakatani Y*, Hirst J. The mechanism of catalysis by type-II NADH:quinone oxidoreductases. Scientific Reports 7:40165, 2017.
Blaza JN, Serreli R, Jones AY, Mohammed K, Hirst J. Kinetic evidence against partitioning of the ubiquinone pool and the catalytic relevance of respiratory-chain supercomplexes. PNAS 111, 2014.
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