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BSc (Biochemistry), University of Alberta, 1975
PhD (Biochemistry), University of Alberta, 1979
Tel: 604-822-5216
Email: brayer@interchange.ubc.ca
The diversity of biological functions expressed by proteins arises
from their different three-dimensional structures. Therefore, the
key to understanding the catalytic action of these macromolecules
is to discover the underlying structure - function relationships that
produce a particular activity. To achieve this goal, our laboratory
is keenly interested in elucidating the high resolution atomic structures
of proteins using X-ray diffraction techniques.
To obtain an even clearer understanding of the mechanistic issues involved
in enzymatic activities, we also pursue the study of protein complexes
with substrates, inhibitors, transition state analogues and even
other proteins. These additional types of studies provide exciting
new information on the functioning of proteins that is not accessible
by other methods. We also obtain further mechanistic insight into
biological function through the combined use of structure-function-mutagenesis
analyses. In this way the controlled and systematic replacement
of key functional and structural amino acids allows for a truly
comprehensive understanding of the roles of individual amino acids.
To assist in this process, structural modeling on molecular graphics
workstations is used to design mutant proteins with specific properties
before they are generated in the laboratory. By combining all the
available structural and functional information, our laboratory
then seeks to apply this knowledge in the development of novel enzyme
inhibitors that have the potential of being human therapeutic drugs.
Overall, the current research effort in our laboratory is focused
on two proteins. The first involves the critical digestive enzyme
human pancreatic alpha-amylase, with the immediate goals of determining
the catalytic mechanism of this enzyme and how substrates bind in
the active site region next to catalytic residues. As part of this
process our laboratory has solved the full three-dimensional atomic
structure of human pancreatic alpha-amylase (see drawing below).
This structural information, in combination with other functional
studies, is being used as the starting point for the design of inhibitors
to act as therapeutic drug agents in the treatment of diabetes,
obesity and dental caries.
A second system being examined involves a unique hexameric form
of the enzyme citrate synthase, which is only found in Gram-negative
bacteria. This key metabolic enzyme is allosterically controlled
by an unknown mechanism. Our laboratory has recently solved the
complete three-dimensional structure of this enzyme (see drawing
below) and begun the process of unraveling the structure-function
relationships that control its catalytic activity. Given the central
role this enzyme plays in the metabolism of Gram-negative pathogens,
understanding its mechanism of action could potentially allow for
the development of novel anti-microbial compounds.
Further details concerning research in our laboratory can be found
in the selected references cited below.
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The Search for Novel Human Pancreatic Alpha-Amylase Inhibitors: High-Throughput Screening of Terrestrial and Marine Natural Product Extracts
Tarling , C.A. , Woods, K., Zhang, R., Brastianos, H.C., Brayer, G.D., Andersen, R.J. and Withers, S.G. ChemBioChem 9, 433-438 (2008)
Alternative Catalytic Anions Differentially Modulate Human Alpha-Amylase Activity and Specificity
Maurus, R., Begum, A., Williams, L.K., Fredriksen, J.R., Zhang, R., Withers, S.G. and Brayer, G.D. Biochemistry 47, 3332-3344 (2008)
Synthesis and Testing of 2-Deoxy-2,2-Dihaloglycosides as Mechanism-Based Inhibitors for Alpha-Glycosidases
Zhang, R., McCarter, J.D., Braun, C., Yeung, W., Brayer, G.D. and Withers, S.G.
J. Organic Chemistry 73, 3070-3077 (2008)
Lumenal Substrate “Brake” on Mucosal Maltase-Glucoamylase Activity Regulates Total Rate of Starch Digestion to Glucose
Quezada-Calvillo, R., Robayo-Torres, C.C., Ao, Z., Hamaker, B.R., Quaroni, A., Brayer, G.D., Sterchi, E.E., Baker, S.S. and Nichols, B.L.
Journal of Pediatric Gastroenterology and Nutrition 45, 32-43 (2007)
The Biological Crystallization Resource: Facilitating Knowledge-Based Protein Crystallizations
Li, C., Kirkwood , K.L. and Brayer, G.D.
Crystal Growth and Design 7, 2147-2152 (2007)
Structural and mechanistic studies of chloride induced activation
of human pancreatic alpha-amylase.
R. Maurus, A. Begum, H.H Kuo, A. Racaza, S. Numao, C. Andersen,
J.W. Tams, J. Vind, C.M. Overall, S.G. Withers, and G.D. Brayer
Protein Science 14, 743-755 (2005)
Acarbose rearrangement mechanism implied by the kinetic and structural
analysis of human pancreatic alpha-amylase in complex with analogues
and their elongated counterparts.
C. Li, A. Begum, S. Numao, K.H. Park , S.G. Withers, and G.D. Brayer
Biochemistry 44, 3347-3357 (2005)
In situ extension as an approach for identifying novel alpha-amylase
inhibitors.
S. Numao, I. Damager, C. Li, T.M. Wrodnigg, A. Begum, C.M. Overall,
G.D. Brayer, and S.G. Withers
J. Biol. Chem. 279, 48282-48291 (2004)
Synthesis and characterisation of novel chromogenic substrates
for human pancreatic alpha-amylase.
I. Damager, S. Numao, H. Chen, G.D. Brayer, and S.G. Withers
Carbohydrate Research 339, 1727-1737 (2004)
Probing the roles of key residues in the unique regulatory NADH
binding site of type II citrate synthase of E. coli .
D.J. Stokell, L.J. Donald, R. Maurus, N.T. Nguyen, G. Sadler, K.
Choudhary, P.G. Hultin, G.D. Brayer, and H.W. Duckworth
J. Biol. Chem. 278, 35435-35443 (2003)
Insights into the evolution of allosteric properties. The NADH
binding site of hexameric type II citrate synthases.
R. Maurus, N.T. Nguyen, D.J. Stokell, A. Ayed, P.G. Hultin, H.W.
Duckworth, and G.D. Brayer
Biochemistry 42, 5555-5565 (2003)
Mechanistic analyses of catalysis in human pancreatic alpha-amylase:
Detailed kinetic and structural studies of mutants of three conserved
carboxylic acids.
E.H. Rydberg, C. Li, R. Maurus, C.M. Overall, G.D. Brayer, and S.G.
Withers
Biochemistry 41, 4492-4502 (2002)
Probing the role of the chloride ion in the mechanism of human
pancreatic alpha-amylase.
S. Numao, R. Maurus, G. Sidhu, Y. Wang, C.M. Overall, G.D. Brayer,
and S.G. Withers
Biochemistry 41, 215-225 (2002)
Comparative analysis of folding and substrate binding sites between
regulated hexameric type II citrate synthases and unregulated dimeric
type I enzymes.
N.T. Nguyen, R. Maurus, D.J. Stokell, A. Ayed, H.W. Duckworth, and
G.D. Brayer
Biochemistry 40, 13177-13187 (2001)
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