Dr. Kevin Ridge

Structural Aspects of G-protein Coupled Receptor Function

The research in my laboratory is primarily focused on the dynamic aspects of integral membrane protein structure. Particular emphasis is given to members of the superfamily of G-protein coupled receptors (GPCR's) sharing the seven-transmembrane-helix structural motif. Biochemical, biophysical, and structural approaches are being used to study the molecular mechanisms underlying GPCR function using the HIV-1 coreceptor CCR5 and the visual photoreceptor rhodopsin as models. Specifically, high-resolution structural methods are being used to elucidate the molecular details of ligand and viral recognition (CCR5) and G-protein mediated signal transduction (rhodopsin, see Figure). It is anticipated that these efforts will have a fundamental impact on our structural understanding of the mechanisms governing signal transfer in these GPCR's while at the same time advancing a general strategy for studying GPCR's involved in other signaling pathways.

A second research area is focused on the development and application of general approaches for the large-scale expression and purification of GPCR's. The main emphasis in these studies is to devise methods that facilitate the optimal expression of properly folded protein in eukaryotic hosts and the one-step generation and purification of native-like, functionally intact receptors for structural studies.

Crystal structures of rhodopsin and the G-protein -subunit highlighting regions implicated in signal transfer.

Selected References

Ridge, K. D., Abdulaev, N. G., Zhang, C., Ngo, T., Brabazon, D. M., and Marino, J. P. (2006) Conformational Changes Associated with Receptor Stimulated Guanine Nucleotide Exchange in a Heterotrimeric G-protein alpha-subunit: NMR Analysis of GTPgammaS-bound States. J. Biol. Chem., January 9 Epub.

Abdulaev, N. G., Karaschuk, G. N., Ladner, J. E., Kakuev, D. L., Yakhyaev, A. V., Tordova, M., Gaidarov, I. O., Popov, V. I., Fujiwara, J. H., Chinchilla, D., Eisenstein, E., Gilliland, G. L., and Ridge, K. D. (1998) Nucleoside Diphosphate Kinase from Bovine Retina: Purification, Subcellular Localization, Molecular Cloning, and Three-dimensional Structure, Biochemistry 37, 13958-13967.

Abdulaev, N. G. and Ridge, K. D. (1998) Light-induced Exposure of the Cytoplasmic End of Transmembrane Helix Seven in Rhodopsin, Proc. Natl. Acad. Sci. USA 95, 12854-12859.

Ladner, J. E., Abdulaev, N. G., Tordova, M., Kakuev, D. L., Ridge, K. D., and Gilliland, G. L. (1999) The Three-dimensional Structures of Two Isoforms of Nucleoside Diphosphate Kinase from Bovine Retina, Acta Crystallogr. D55, 1127-1135.

Ridge, K. D., Ngo, T., Lee, S. S. J., and Abdulaev, N. G. (1999) Folding and Assembly in Rhodopsin: Effect of Mutations in the Sixth Transmembrane Helix on the Conformation of the Third Cytoplasmic Loop, J. Biol. Chem. 274, 21437-21442.

Abdulaev, N. G. and Ridge, K. D. (2000) Heterologous Expression of Bovine Opsin in Pichia pastoris, in Vertebrate Phototransduction and the Visual Cycle, Methods in Enzymology, (K. Palczewski, Ed.), Vol. 315, pp. 3-11.

Ridge, K. D. and Abdulaev, N. G. (2000) Folding and Assembly of Rhodopsin from Expressed Fragments, in Vertebrate Phototransduction and the Visual Cycle, Methods in Enzymology, (K. Palczewski, Ed.), Vol. 315, pp. 59-70.

Abdulaev, N. G., Kakuev, D. L., and Ridge, K. D. (2000) Bovine Retinal Nucleoside Diphosphate Kinase: Biochemistry and Molecular Cloning, in Vertebrate Phototransduction and the Visual Cycle, Methods in Enzymology, (K. Palczewski, Ed.), Vol. 316, pp. 87-100.

Abdulaev, N. G., Ngo, T, Lu, Z., and Ridge, K. D. (2000) Functionally Discrete Mimics of Light-activated Rhodopsin Identified Through Expression of Soluble Cytoplasmic Domains, J. Biol. Chem. 275, 39354-39363.

Abdulaev, N. G., Strassmaier, T. T., Ngo, T., Chen, R., Luecke, H., Oprian, D. D., and Ridge, K. D. (2002) Grafting Segments from the Extracellular Surface of CCR5 onto a Bacteriorhodopsin Transmembrane Scaffold Confers HIV-1 Coreceptor Activity, Structure 10, 515-525.

Rao, N. M., Silin, V., Ridge, K. D., Woodward, J., and Plant, A. L. (2002) Cell Membrane Hybrid Bilayers Containing the G-protein Coupled Receptor CCR5, Anal. Biochem. 307, 117-130.

Ridge, K. D. (2002) Algal Rhodopsins: Phototaxis Receptors Found at Last, Curr. Biol. 12, R588-R590.

Brabazon, D. M., Abdulaev, N. G., Marino, J. P., and Ridge, K. D. (2003) Evidence for Structural Changes in Carboxyl-terminal Peptides of Transducin alpha-subunit upon binding a Soluble Mimic of Light-activated Rhodopsin, Biochemistry 42, 302-311.

Ridge, K. D., Abdulaev, N. G., Sousa, M., and Palczewski, K. (2003) Phototransduction: crystal clear, Trends Biochem. Sci. 28, 479-487.

Abdulaev, N. G., Zhang, C., Dinh, A., Ngo, T., Bryan, P. N., Brabazon, D. M., Marino, J. P. and Ridge, K. D. (2005) Bacterial Expression and One-step Purification of an Isotope-labeled Heterotrimeric G-protein alpha-subunit, J. Biomol. NMR 32, 31-40.