We are offering an opportunity to engage in an exciting PhD project that combines biophysical, biochemical and state-of-the art structural investigation of a unique class of ligand-gated membrane channel receptors from insects. These odorant receptors enable insects to exhibit an unmatched sense of smell that is critical to how mates are attracted, food sources identified and hosts located. Insect odorant receptors are complexes of an ion channel-forming subunit, Orco and one of a family of highly divergent odorant “tuning” receptors, OrX (61 to 341 depending on the insect species). A complex of these two subunits with as-yet unknown stoichiometry (German et al., 2013) is capable of both ionotropic and metabotropic signalling (Carraher et al., 2015). The PhD project will aim to reveal for the first time the 3-D organization and architecture of the Orco/OrX complex and the structural basis for how Orco can couple with so many diverse OrX partners.
You will use our established cell-based and cell-free expression approaches to prepare Orco and OrX homomeric and heteromeric complexes in artificial membrane-like environments (Carraher et al., 2013). These will be subject to a variety of biophysical studies to confirm correct folding and subunit stoichiometry and complex size. 3-D structures of the homomeric (Orco) and heteromeric complexes (Orco/Orx) will be generated by single-particle cryo-EM analysis to reveal individual structures and protein-protein intercation at the highest resolution (Radjainia et al. 2010, 2015). This endeavour will utilize the capabilities of a high-resolution 200kV Transmission Electron Microscope (TEM) equipped with field emission gun enabling state-of-the art ultra-high-resolution image acquisition. This microcsope, newly installed at the School of Biological Sciences, is the first of its kind in NZ.
This project will suit someone with a strong background in molecular biology, protein biochemistry or structural biology, who is keen to participate in the state-of-the-art structural analysis of membrane proteins. There is a strong prospect of securing funding to support a 3-year PhD stipend; however, the prospective student is expected have grades sufficient for him or her to attract an University of Auckland doctoral fellowship, if necessary. The project will be a collaboration between Assoc Prof Alok Mitra (SBS) and Dr Andrew Kralicek and Dr Colm Carraher from Plant & Food Research. For more information please contact Assoc Prof Mitra or Dr Andrew Kralicek
Assoc Prof Alok Mitra
School of Biological Sciences
University of Auckland
Phone: +64-9-923 8162
Email: [email protected]
Dr Andrew Kralicek
Science Team Leader
Molecular Sensing Team
Plant & Food Research
Email: [email protected]
Carraher C, Newcomb RD, Kralicek AV (2013) The recombinant expression, detergent solubilisation and purification of insect odorant receptor subunits. Protein Expr. Purif. 90:160-169.
Carraher C, Dalziel J, Jordan M, Christie DL, Newcomb RD, Kralicek AV (2015) Towards an understanding of the structural basis for insect olfaction by odorant receptors. Insect Biochem. Mol. Biol. (Accepted for publication).
German PF, van der Poel S, Carraher C, Kralicek AV, Newcomb RD (2013) Insights into subunit interactions within the insect olfactory receptor complex using FRET. Insect Biochem Mol Biol. 43: 138-145.
Mazdak Radjainia, Hariprasad Venugopal, Ambroise Desfosses, Amy Phillips, Amy Yewdall, Mark Hampton, Juliet Gerrard, and Alok K. Mitra. (2015). Cryo-EM structure of human peroxiredoxin-3 filament reveals the assembly of a putative chaperone. Structure. Apr 22. pii: S0969-2126(15)00123-9. doi: 10.1016/j.str.2015.03.019.
Radjainia, M., Hyun, J-K., Leysath, C. E., Leppla, S. H. and Mitra, A. K. (2010) An anthrax toxin-neutralizing antibody reconfigures the protective antigen heptamer into a supercomplex. Proc. Natl. Acad. Sci. USA. 107:14070-14074.