Mohammad Mazhab-Jafari

At A Glance

• Electron cryo-microscopy (cryoEM) application in high-resolution structural biology.
• Mammalian target of rapamycin complex 1 and 2 signaling pathways.
• Scaffold proteins.
• Affinity-cryoEM method development for study of scarce and post-translationally modified protein complexes.

Short Bio

• B.Sc from McMaster University in 2006 with genetic engineering specialization.
• M.Sc in 2008 from the laboratory of Prof. Giuseppe Melacini at McMaster university studying the allosteric pathways in cyclic nucleotide binding domains with solution nuclear magnetic resonance (NMR) spectroscopy.
• Ph.D in 2014 from the laboratory of Prof. Mitsuhiko Ikura at U of T using X-ray crystallography and solution NMR to uncover nucleotide hydrolysis mechanism and membrane interactions of small GTP binding proteins involved in cancer.
• Post doctoral research in electron cryo-microscopy (cryoEM) in the laboratory of Prof. John Rubinstein at SickKids research institute elucidating the high-resolution structure of the membrane embedded region of a eukaryotic vacuolar-type ATPase involved in metastatic bone cancer.

Research Synopsis

Our research focuses on elucidating the structure and function of macromolecular assemblies that regulate cellular growth using electron cryo-microscopy (cryoEM) as a primary tool. Recent advances in sample preparation, direct electron detector devices, and image processing algorithms have made cryoEM the method of choice to study large and conformationally heterogenous complexes that can only be obtained at low abundance. The focus of my lab will be on complexes involved in mammalian target of rapamycin (mTOR) signaling, specifically mTOR complex 1 and 2 and tuberous sclerosis complex (TSC). We will biochemically purify these molecular machines from both immortal human cell lines such as HEK293F cells and model organisms yeast S. cerevisiae and S. pombe. The structural knowledge gained from the endogenous complexes will facilitate design of agonist and antagonist that may modulate the aberrant function of proteins harbouring disease mutations.

In addition to conventional protein expression and purification, our group will develop affinity-based electron microscopy grids that will enable direct capture of endogenous protein complexes from cell lysate. Affinity-based capture will allow for rapid purification of endogenously expressed complexes for cryoEM analysis. This platform will be used to study the conformational and compositional dynamics of regulatory scaffolding proteins such as kinase suppressor of Ras 1 (KSR1). The shorten time of purification is critical to preserve the native state of highly dynamic multi-component molecular complexes.

Graduate Students

Jennifer Lou
Naimul Hasan
David Dai
Elnaz Khalili Samani
Ruhma Masud