Much of our work here is aimed at understanding the molecular and structural underpinnings of the generation of cellular electricity. All such phenomena - from the nerve action potential, to sensory transduction, to control of processes as varied as muscle contraction, hormone secretion, or blood volume homeostasis - are ultimately mediated by a single class of membrane proteins: the ion channels. We seek to understand the molecular mechanisms by which ion channel proteins open and close to switch the flows of ions across cellular membranes, and by which the open pore is able to choose so exquisitely which ions are able to permeate. Cellular electrical behavior requires ion gradients across biological membranes, and these gradients must be established by energy-consuming "transporter" proteins, which move ions "uphill." Our group also studies the mechanisms of transporters.
The lab focuses on channels and transporters that are approachable by a combination of attacks in reduced, biochemically defined systems. We use a combination of electrophysiological analysis, single-channel recording, membrane biochemistry, and x-ray crystallography to attack these problems, and each student is expected to gain experience in all these methods. Current efforts are directed at CLC Cl–-transporting proteins as well as a newly discovered subclass of these that specifically handle the cytotoxic F– ion. Our new interest in F- exporting proteins has also led us to stumble upon a phylogenetically unrelated and very unusual class of F–-specific ion channel proteins.
A few years ago, we discovered, to our shock and awe, that a bacterial homologue of CLC channels is not itself an ion channel, but rather functions as an ion "pump," stoichiometrically exchanging Cl- on one side of the membrane for H+ on the other. Using a combination of electrophysiology, membrane reconstitution, and x-ray crystallography, we are endeavoring to understand how these transport proteins work and also to comprehend the wider mechanistic implications of this co-habitation within the same molecular family of such fundamentally different ion-transport mechanisms.
Brammer, A., Stockbridge, R.B., and Miller, C. 2014. F-/Cl- selectivity in CLCF-type F-/H+ antiporters. J. Gen Physiol. 144:129-136. doi 10.1085/jgp.201411225
Ji, C., Stockbridge, R.B., and Miller, C. 2014. Bacterial fluoride resistance, Fluc channels, and the weak acid accumulation effect. J. Gen. Physiol. 144:257-261. doi: 10.1085/jgp.201411243
Tsai, M.-F., Jiang, D., Zhao, L., Clapham, D.E., and Miller, C. 2014. Functional reconstitution of the mitochondrial Ca2+-H+ antiporter Letm1. J. Gen. Physiol. 143:67-73. doi10.1085/jgp201311096
Stockbridge, R.B., Robertson, J.L., Kolmakova-Partensky, L., and Miller, C. 2013. A family of fluoride- specific ion channels with dual-topology architecture. eLife 2013:2:e01084,
Lim, H.-H., Stockbridge, R.B., and Miller, C. 2013. Fluoride-dependent interruption of the transport cycle of a CLC Cl-/H+ exchanger. Nature Chem. Biol. 9:721-725.
Tsai, M-F. and Miller, C. 2013. Substrate selectivity in arginine-dependent acid resistance in enteric bacteria. Proc Natl. Acad. Sci. USA 110:5893-5897
Tsai, M-F., McCarthy, P., and Miller, C. 2013. Substrate selectivity in glutamate-dependent acid resistance in enteric bacteria. Proc Natl. Acad. Sci. USA 110:5898-5902.
Lim, H.H., Shane, T., and Miller, C. 2012. Intracellular proton access in a Cl-/H+ antiporter. PLoS Biol.10:1-8
Stockbridge, R., Lim, H.H, Otten, R., Williams, C., Shane, T., Weinberg, Z., and Miller, C. 2012. Fluoride resistance and transport by riboswitch-controlled CLC antiporters. Proc. Natl. Acad. Sci. USA 109:15289-15294.
Tsai, M-F., Fang, Y., and Miller, C. 2012. Sided functions of an arginine-agmatine exchange-transporter oriented in lipsomes. Biochemistry 51:1577-1585.
Piasta, K.N., Theobald, D.L., and Miller, C. 2011. Potassium-selective block of barium permeation through single KcsA channels. J Gen Physiol 138:421-436.
Clapham, D.E. and Miller, C. 2011. A thermodynamic framework for understanding temperature sensing by transient receptor potential (TRP) channels. Proc Natl Acad Sci U S A 108:19492-19497.
Structure of a slow CLC Cl-/H+ antiporter from a cyanobacterium. Jayaram, H, Robertson, J.L. Wu, F., Williams, C., and Miller, C. 2011. Biochemistry 50:788-794.
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Last reviewed: September 15, 2014