Molecular determinants of ion conduction and inactivation in k- channels.
Kukuljan, Manuel, Pedro Labarca, and Ramon Latorre.
Departamento de Fisiologia, Facultad de Ciencias, Universidad de
Valparaiso, and, Centro de Estudios Cient[acute]ificos de Santiago, Casilla
19443, Santiago 9, and Departamento de Biolog[acute]ia, Facultad de Ciencias,
Universidad de Chile, Santiago
APStracts 2:0023C, 1995.
Potassium channel-forming proteins can be grouped in three families that
differ by the number of potential membrane spanning segments. The largest of
these families is composed by tetrameric channels with subunits containing 6
putative membrane spanning segments (S1-S6). Inward rectifiers comprise a
second family of potassium channels with subunits having 2 transmembrane
domains (M1, M2). Monomers in the third family are proteins containing only
one membrane spanning segment and they give origin to min-K channels. Joining
together segments S5 and S6 in the case of voltage-gated potassium channel,
and M1 and M2 in inward rectifiers, there is a highly conserved region with
the shape of a hairpin called the H5 or P-region. The P-region, the loop
connecting the S4 and S5 domains and the S6 transmembrane segment in Shaker
-type K- channels and the C-terminal in inward rectifiers appears to play
crucial roles in ion conduction. In Shaker K- channels the N-terminus has
been identified as responsible of the fast inactivation (N-type of
inactivation). If the fast inactivation gate is removed, a slower
inactivation process persists and its rate can be altered by mutations of
amino acid residues forming part of the region in the neighborhood of the C
-terminal (C-type inactivation). In this review we discuss the strategies
followed to identify the different structures of potassium channel involved
in ion conduction and inactivation processes and how they interplay.
Received 1 January 1993; accepted in final form 2 January 1994
APS Manuscript Number C566-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1994 The American Physiological Society.
Published in APStracts on 27 February 1995.