Our Science – Guy Website

H. Robert Guy, Ph.D.

Laboratory of Cell Biology Head, Computational Structural Biology Section Senior Investigator National Cancer Institute Building 12B, Room B102 12 South Drive Bethesda, MD 20892 Phone:   301-496-2068 Fax:   301-402-4724 E-Mail:   bg4y@nih.gov

Biography

Dr. Guy obtained his Ph.D. in biophysics from the University of Illinois where he used electrophysiological methods to study postsynaptic receptors in neurons. He began to develop models of membrane channel structures during his postdoctoral fellowship at the State University of New York at Albany. His most notable work involves modeling the three-dimensional structure and functional mechanisms of voltage-gated and mechanosensitive ion channels.

Research

Structural Modeling of Membrane Channel Proteins

The primary goals of our group are to develop procedures to model the three-dimensional structures of membrane proteins and to use these procedures to develop models of specific proteins. Most of our current work concentrates on superfamilies of ion channel proteins for which a crystal structure of at least one member has been determined. Our most noted work has been on potassium channels and proteins, such as sodium and calcium channels, that evolved from them. The recent determination of a crystal structure of a bacterial potassium channel allows us to better evaluate our methods and results, and lets us move on to a more precise level of molecular modeling. Our early models of the channel protein's secondary structure, its transmembrane topology, and the general location and orientation of the pore forming segments and predictions about which portions of the protein form the ion selective region, voltage sensor for activation gating, the inactivation gate, and binding sites for a variety of drugs and toxins have been confirmed. However, atomic scale models of large proteins that are not constrained by precise structural data always contain errors. The crystal structure allows us to correct these errors for the highly conserved ion selective portion of the potassium channels. Based on this new information, we are currently extending our models to numerous membrane proteins that are homologous to the potassium channel that was crystallized or that may have structures similar to it. These include not only numerous families of potassium channels, but also sodium, calcium, and cyclic nucleotide-gated channels, ionotrophic glutamate receptors, and some types of potassium transport proteins. We are also examining conformational changes in these proteins and have used computer graphic and computational chemistry methods to develop models of the entire transmembrane portion of the several potassium channels in closed, open, and inactivated conformations. These models are supported by results of many mutagenesis experiments obtained from numerous groups. We have also worked on mscL, which forms mechanosensitive channels in bacterial membranes. This project exemplifies how we use molecular modeling to augment experimental studies of the structure and functional mechanisms of membrane proteins. Beginning with the crystal structure of a closed conformation of mscL from M. tuberculosis, we: (1) developed models of the N terminus which was unresolved in the crystal structure; (2) developed homology models of mscL from Escherichia coli; (3) developed models of the conformational changes involved in opening the channels; and (4) used mutagenesis experiments on Escherichia coli mscL to test these models.


Collaborations include Peter Backx, Toronto University; Evert Bakker, Universitat Osnabruck; Stewart Durell, NIH; Saul Goldman, Guelph University; Tatsunosuka Nakamura, Chiba University; Sergei Sukharev, University of Maryland; and Gea-Ny Tseng, Virginia Commonwealth University.

This page was last updated on 8/25/2008.