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Contact: Dean Chris Comer
LA 136, Missoula, MT 59812
Telephone: 243-2632
Fax: 406-243-4076

Office Location: CHEMISTRY 217
Office Telephone: 406 243 6028
E-mail: stephen.sprang@mso.umt.edu

Current Position:

 Director, Center for Biomolecular Structure and Dynamics

Professor, Division of Biological Science

Associated Faculty Member, Department of Chemistry

Field Of Study:

Structural Biology and Biochemistry: Biological Signal Transduction

Research Interests:

We study the structural chemistry of signal transduction, particularly as mediated by heterotrimeric G proteins. Experimental approaches include x-ray crystallography, enzymology and spectroscopy. We also use Molecular Dynamics simulations to better understand the conformational changes that occur in G proteins and their effectors.  The following is a brief summary of ongoing research projects. Names of Lab members are italicized; for more information, see the links to their publications in the narrative below.

What is the mechanism by which GTP hydrolysis is coupled to conformational transitions in G proteins?

It is this chemical process that is linked to the termination of signaling activity. Earlier work in the lab focused on structural studies of relevant conformational states of G protein a subunits in the GTP, GDP•Pi and GDP•AlF4--bound forms of the enzyme. More recent work has focused on structural and mutational analysis of a subunits with interesting catalytic properties and  ¹⁸O kinetic isotope experiments to characterize the chemical structure of the transition state for GTP hydrolysis in various members of the G protein superfamily. 

How do G proteins regulate effectors - how do effectors regulate G proteins?

When bound to GTP, G proteins regulate the activity of signaling molecules called effectors. Effectors may have reciprocal effects on G proteins, most commonly by accelerating GTP hydrolysis (thereby leading to dissociation of the G protein from its effector). Earlier work addressed the regulation of adenylyl cyclase by Gas,

and more recently, the mechanism by which Ga13 regulates G-protein dependent regulators of cytoskeleton formation. These remarkable effectors activate the small G protein, Rho.  At the same time, these effectors deactivate Ga13, resulting in tightly coupled cycles of G-protein activation and deactivation.

How are Ga proteins activated? How is activation prevented?

 

Just as the signaling activity of G protein a subunits is terminated by GTP hydrolysis, it is initiated by GTP binding. GDP dissociation is the kinetic barrier to this process. Our laboratory has studied the mechanism by which GDP dissociation is inhibited by G protein bg heterodimers,  and by the cytosolic, GoLoco-motif containing protein AGS3,  Efforts are also underway to determine the structure of the cytosolic exchange factor, RIC-8, in complex with various G protein a subunits.  

Education:

 B.S. in Biochemistry from California State University of Los Angeles in 1971

Ph.D. in Biochemistry from the University of Wisconsin, Madison in 1977

Postdoctoral studies with Robert Fletterick at the University of Alberta and the University of California at San Francisco, 1978-1983

Selected Publications:

Mou, T.C., Gille, A., Fancy, DA, Seifert, R and Sprang, S.R.,  (2005) “Structural basis for the inhibition of mammalian adenylyl cyclase by 2’(3’)-O-(N-methylanthraniolyl)-guanosine 5’-triphosphate”  Journal of Biololgical Chemistry, 280:7253-61

 Chen, Z., Singer, W.D., Sternweis, P.C. and Sprang, S. R. “Structure of the p115rhoGEF rgRGS domain of-Ga1/i1 chimera complex suggests convergent evolution of a GTPase activator “ (2005), Nature Structural and Molecular Biology, 12:191-7

 

Sinha, S.C., Wetter, M., Schultz, Sprang, S. and Linder, J (2005) “Asymmetry in Homodimeric Adenylyl Cyclases: Structures of the Mycobacterium  tuberculosis Rv 1900c”  EMBO Journal, 24:663-73

 

Davis, T.,  Bonacci, T.M., Smrcka, AV. and Sprang, S.R. (2005) “Structural and Molecular Characterization  of a Preferred Protein Interaction Surface on G Protein bg Subunits” (2005) Biochemistry 44:10593-10604

 

 Ja, W.W., Adhikari, A., Austin, R.J., Sprang, S.R., Roberts, R.W.(2005) “A peptide core motif for binding to heterotrimeric G protein a subunits”  Journal of Biological Chemistry, 280:32057-32060

 

Mou, T-C, Gille, A., Suryanarayana, S.,Richter, M., Seifert, R. and Sprang, S.R.(2006) “Broad Specificity of Mammalian Adenylyl Cyclases for Interaction with 2’,3’-Substituted Purine-and Pyrimidine Nucleotide Inhibitors”  Molecular Pharmacology,70:878-886

 

Sinha, S.C. and Sprang, S. (2006) “Structures, mechanism, regulation and evolution of class III nucleotidyl cyclases” Reviews of Physiology, Biochemistry and Pharmacology 157:105-140

 

Sprang, S.R., Chen, Z and Du, X. (2007)“Structural basis of effector regulation and signal termination in heterotrimeric Ga proteins” Advances Prot. Chem. 74:1-65

Du, X., Ferguson, K., Gregory, R. and Sprang, S.R. (2008) “A method to determine ¹⁸O kinetic isotope effects in the hydrolysis of nucleotide triphosphates” Analytical Biochemistry 372:213-21

 

Sprang, S. (2007) “A Receptor Unlocked”, Nature, 450, 355-6

Publications:

Coleman, D. E.,  Berghuis, A., Lee, E., Gilman, A. and Sprang, S. (1994). Structures of active conformations of Gi_a1 and the mechanism of GTP hydrolysis.  Science 265:1405-1412.

Naismith, J. H., Devine, T. Q., Brandhuber, B. J. and Sprang, S. R. (1995).  Crystallographic evidence for dimerization of unliganded tumor necrosis factor receptor.  Journal of Biological Chemistry 270:13303-13307.

Sutton, R. B., Davletov, B.A., Berghuis, A. M., Südhof, T. C. and Sprang, S. R. (1995).Structure of the first C₂-domain of synaptotagmin I: A novel Ca²⁺/phospholipid binding fold.  Cell 80:929-938

Wall, M. A., Coleman, D. E., Lee, E., Iñiguez-Lluhi, J. A., Posner, B. A., Gilman, A. G. and Sprang, S. R. (1995).  The structure of the G protein heterotrimer G_iab1g2. Cell 80:1047-105

Tesmer, J. J. G., Berman, D. M., Gilman, A. G. and Sprang, S. R. (1997).  Structure of RGS4 bound to AIF₄^-- activated G_ia1: Stabilization of the transition state for GTP hydrolysis.  Cell 89:251-261

Sprang, S. R. (1997).  G Protein Mechanisms: Insights from structural analysis. Annual Review of Biochememistry 66:639-678. 

Tesmer, J. J. G., Sunahara, R. K., Gilman, A. G. and Sprang, S. R. (1997).  Crystal structure of the catalytic domains of adenylyl cyclase in a complex with G_sa•GTPgS. Science 278:1907-1916

Tesmer, J.J.G., Sunahara, R.K., Johnson, R.A., Gosselin G., Gilman, A.G., and Sprang, S.R (1999) Two metal ion catalysis in adenylyl cyclase revealed by its complexes with ATP analogs, Mg²⁺, Mn²⁺ and Zn²⁺. Science 285:756-760.

Xiao, T, Towb P., Wasserman, S.A. and Sprang, S.R. (1999) Three-Dimensional Structure of a Complex between the Death Domains of Pelle and Tube. Cell 99: 545-555. 

Du, X, Black, G., Lecchi, P., Abramson, F. and Sprang, S.R. (2004) “Kinetic Isotope Effects in Ras-catalyzed GTP Hydrolysis: Evidence for a Loose Transition State” Proceedings of the National Academy of Sciences, USA 101, 8858-63