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The Structure of the Potassium Channel: Molecular Basis of K

Summary: The Structure of the Potassium
Channel: Molecular Basis of K
Conduction and Selectivity
Declan A. Doyle, Joa~ o Morais Cabral, Richard A. Pfuetzner,
Anling Kuo, Jacqueline M. Gulbis, Steven L. Cohen,
Brian T. Chait, Roderick MacKinnon*
The potassium channel from Streptomyces lividans is an integral membrane protein with
sequence similarity to all known K channels, particularly in the pore region. X-ray
analysis with data to 3.2 angstroms reveals that four identical subunits create an inverted
teepee, or cone, cradling the selectivity filter of the pore in its outer end. The narrow
selectivity filter is only 12 angstroms long, whereas the remainder of the pore is wider
and lined with hydrophobic amino acids. A large water-filled cavity and helix dipoles are
positioned so as to overcome electrostatic destabilization of an ion in the pore at the
center of the bilayer. Main chain carbonyl oxygen atoms from the K channel signature
sequence line the selectivity filter, which is held open by structural constraints to co-
ordinate K ions but not smaller Na ions. The selectivity filter contains two K ions about
7.5 angstroms apart. This configuration promotes ion conduction by exploiting electro-
static repulsive forces to overcome attractive forces between K ions and the selectivity
filter. The architecture of the pore establishes the physical principles underlying selective
K conduction.


Source: Akabas, Myles - Department of Physiology and Biophysics, Albert Einstein College of Medicine, Yeshiva University
Alford, Simon - Department of Biological Sciences, University of Illinois at Chicago
Chait, Brian T. - Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, Rockefeller University
Economou, Tassos - Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology, Hellas
Huettner, James E. - Department of Cell Biology and Physiology, Washington University in St. Louis


Collections: Biology and Medicine