Professor Emeritus

Emil Pai

PhD, Universitat Heidelberg (FRG)

Medical Sciences Building
1 KIng's College Circle, Room 5358 , Toronto, Ontario Canada M5S 1A8
Research Interests
Biomedical Imaging, Data Science and Computational Biology, Structural Biology

Research Synopsis

Structure and Function of Proteins

Knowledge of the three-dimensional structure of a given protein is an absolutely essential prerequisite for the full understanding of the chemical basis of an enzyme’s catalytic mechanism, for interpreting the way structural proteins like e.g. actin interact with each other or how lead compounds have to be modified to improve affinity and specificity of drug candidates. In my lab, we use X-ray crystallographic techniques to establish the molecular architectures of proteins. We integrate our structural results with biochemical and molecular-biological as well as computational data, either collected in our laboratory or available through collaborations with specialists in the respective fields.

Orotidine 5'-phosphate decarboxylase from archaea, plasmodia and man
ODCase is one of the most proficient enzymes known. It catalyzes the conversion of orotidine-5'-mono-phosphate (OMP) to UMP, the last step in the de novo biosynthesis of pyrimidine nucleotides enhancing the decarboxylation rate by 17 orders of magnitude without the help of any cofactors or metal ions. We have determined more than 50 structures of the various enzymes, apo-forms as well as complexes with substrate, product and a large number of inhibitors synthesized and tested in animals as antimalaria and anti-cancer agents by our collaborators in medicinal chemistry, parasitology and cancer research.

CorA -- a Mg 2+ transporter from T. maritima
Represents the lab’s first membrane protein structure, a pentameric protein that imports Mg2+-ions into the cell. While our lab pursues the structures of the “open” state of the molecule and structurally characterizes a large number of mutants, we also collaborate with colleagues specializing in electrophysiology, AFM and computational approaches to elucidate the details of the protein’s workings.

Antibodies as tools in structure research
Although the three-dimensional structure of antibodies has been know for a long time, they still represent interesting research targets as well as unique tools for stabilizing transitional states. Weare interested in the structural basis of antibody maturation, crossreactivity,
and the recognition of epitopes on HIV proteins. We also make use of antibodies in trapping intermediates of the PrPC-PrPSc transition of prion proteins for structural characterization.

Recent Publications

  • K. Okamoto, K. Matsumoto, R. Hille, B.T. Eger, E.F. Pai & T. Nishino (2004) Crystal Structure of Xanthine Oxidoreductase in Catalysis: Hydroxylation Mechanism and Inhibition. Proc. Natl. Acad. Sci. USA, 101:7931-7936.
  • M. Fujihashi, A.M. Bello, E. Poduch, L. Wei, S.C. Annedi, E.F. Pai & L.P. Kotra (2005) An Unprecedented Twist to ODCase Catalytic Activity. J. Amer. Chem. Soc. 127:15048-15050.
  • J. Payandeh & E.F. Pai (2006) A Structural Basis for Mg2+ Homeostasis and the CorA Translocation Cycle. EMBO J. 25:3762-3773.
  • A.M. Bello, E. Poduch, M. Fujihashi, M. Amani, Y. Li, I. Crandall, R. Hui, P.I. Lee, K.C. Kain, E.F. Pai & L.P. Kotra (2007) A Potent, Covalent Inhibitor of Orotidine 5’-Monophosphate Decarboxylase with Antimalarial Activity. J. Med. Chem. 50:915- 921.

Graduate Students

Jennifer Chiang
Shekeb Khan
Braden Sweeting (Co-supervised)