2. K,K,K,at atom 2829,2830,2831,
3. about 36 einstron
4.the spacefill parts: red for Gly79 ,yellow for Tyr78, orange for Gly77 ,
Science 1998 Apr 3;280(5360):69-77
The structure of the potassium channel: molecular basis
of
K+ conduction and selectivity.
Doyle DA, Morais Cabral J, Pfuetzner RA, Kuo A, Gulbis
JM, Cohen SL, Chait BT,
MacKinnon R
Laboratory of Molecular Neurobiology and Biophysics and
the Howard Hughes Medical
Institute, Rockefeller University, 1230 York Avenue,
New York, NY 10021, USA.
abstract
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.
3. ISRS:A ASN 153 THR 179
GLU 209 LEU 219
ISRS:B ASN 153 THR 179
GLU 209 LEU 219
4.
