The long-range goal of this project is to understand the molecular basis of selective ion conduction in potassium channels. A gating-modified version of a Shaker potassium channel from Drosophila melanogaster will be expressed in Xenopus oocytes and studied using electrophysiological techniques. The research focuses on a short segment of the ion channel protein which was recently found to be an integral structural component of the ion conduction pathway. Using site-specific mutagenesis, the pore-forming region of the protein will be altered and the functional consequences studied. Inhibitory ions will be used in conjunction with mutagenesis of the channel to probe the structure of the ion conduction pore. Specific hypotheses about the way-inhibitory and conducting ions may interact with chemical groups in the pore will be tested. This study will lead to a better understanding of the molecular basis of ion selectivity in potassium channels. Because potassium channels are related to the sodium and calcium channels, some of the general principles learned in this study may be applicable to those ion channels as well. Potassium channels are key molecular elements involved in the generation of electrical signals in neurons and other cells. This project is health-related because a better understanding of the structure and function of these membrane proteins may open the way, in the future, to the development of pharmacological agents directed against potassium channels.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Physiology Study Section (PHY)
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Harvard University
Schools of Medicine
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Valiyaveetil, Francis I; Sekedat, Matthew; Mackinnon, Roderick et al. (2004) Glycine as a D-amino acid surrogate in the K(+)-selectivity filter. Proc Natl Acad Sci U S A 101:17045-9
Zhou, Yufeng; MacKinnon, Roderick (2004) Ion binding affinity in the cavity of the KcsA potassium channel. Biochemistry 43:4978-82
Zhou, Ming; MacKinnon, Roderick (2004) A mutant KcsA K(+) channel with altered conduction properties and selectivity filter ion distribution. J Mol Biol 338:839-46
Zhou, Yufeng; MacKinnon, Roderick (2003) The occupancy of ions in the K+ selectivity filter: charge balance and coupling of ion binding to a protein conformational change underlie high conduction rates. J Mol Biol 333:965-75
Yifrach, Ofer; MacKinnon, Roderick (2002) Energetics of pore opening in a voltage-gated K(+) channel. Cell 111:231-9
Gulbis, J M; Zhou, M; Mann, S et al. (2000) Structure of the cytoplasmic beta subunit-T1 assembly of voltage-dependent K+ channels. Science 289:123-7
Jiang, Y; MacKinnon, R (2000) The barium site in a potassium channel by x-ray crystallography. J Gen Physiol 115:269-72
Gulbis, J M; Mann, S; MacKinnon, R (1999) Structure of a voltage-dependent K+ channel beta subunit. Cell 97:943-52
Roux, B; MacKinnon, R (1999) The cavity and pore helices in the KcsA K+ channel: electrostatic stabilization of monovalent cations. Science 285:100-2
Morrill, J A; MacKinnon, R (1999) Isolation of a single carboxyl-carboxylate proton binding site in the pore of a cyclic nucleotide-gated channel. J Gen Physiol 114:71-83

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