Ion channel gating and selectivity
All cells use selective transport of molecules across their membranes to maintain nutrient homeostasis and to support cellular signaling. Ion channels are found in all three domains of life and are used to modulate the cellular membrane potential and the proton-motive force. The largest family of channels is the tetrameric cation channels, including those for Na+, K+ and Ca2+ ions, which have two basic functional properties. They selectively conduct particular ions and they gate open or closed in response to stimuli. Together, these two processes control how rapidly the membrane potential changes, driving a wide-range of physiological processes. The overarching goal of this research project is to determine molecular mechanisms by which ion selectivity and gating are integrated into a concerted output, representing the sum total ion conduction across the membrane.
Mapping regulatory sites in networks of signaling and metabolic proteins
Genetics, site-directed mutagenesis and/or structure determination has been the primary means to identify regulatory molecules and their targets, but these approaches are each severely limited by practical considerations, e.g., observable phenotypes, functional assays, and protein expression. We overcame many of these problems by developing an approach to use compensatory mutations discovered within and between proteins in the exploding genome databases. The basic principle is that sites that influence each other are co-constrained throughout the evolution of the protein family. This approach not only identifies known allosteric sites in proteins, but also was used previously to predict novel regulatory sites that we validated as important for the protein’s function. When the same approach was employed to examine co-evolution between proteins, we identified proteins known to interact with one another in both stable and transient complexes. The overarching goal of this research project is to learn the rules that underlie the complex network of functional connections between signaling and metabolic proteins in cells, with one goal being to identify novel connections between cellular components.