2. 39.66 A
3. K. K. K(red)
4. Gly79 and Tyr78
gray: Gly79; red:Tyr78
Problem 2
title: The Structure of the Potassium Channel: Molecular
Basis of K+ Conduction and
Selectivity
Author:Declan A. Doyle, Joã Morais Cabral, Richard
A. Pfuetzner, Anling Kuo, Jacqueline
M. Gulbis, Steven L. Cohen, Brian T. Chait, and Roderick MacKinnon
Journal:Science. 1998 Apr 3;280(5360):69-77. PMID: 9525859;
UI: 9819202.
Abstract
Laboratory of Molecular Neurobiology and Biophysics and the Howard
Hughes Medical
Institute, Rockefeller University, 1230 York Avenue, New York, NY 10021,
USA. 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 coordinate 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 electrostatic 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.
Comments: Comment in: Science 1998 Apr 3;280(5360):56-7 Comment in:
Science 1998 Aug
14;281(5379):883 Comment in: Science 1998 Aug 21;281(5380):1146 PMID:
9525859, UI:
98192802
Problem 3
1. 1RSR
2. 2 helices; 2 beta sheets
3. Asn153--> Thr179; Glu209-->Leu219
4. figure
analysis
