Structural determinant for assembly of mammalian K+ channels.
K+ channel function is regulated through the assembly of channel subunit isoforms into either homo- or heterotetrameric structures each characterized by distinct pharmacologic and kinetic properties. In studying the molecular basis of subunit association in mammalian Shaker-like K+ channels, we constructed deletion mutants of the inactivating K+ channel hKv1.4 alone and in tandem with hKv1.5 and examined the functional properties electrophysiologically in Xenopus oocytes. Deletion of 255 amino acids in the amino-terminal domain of hKv1.4 prevented the formation of hybrid channels within the subfamily but had no effect on homomultimerization or voltage-dependent gating. The amino-terminal deletion mutant of Kv2.1, a noninactivating K+ channel from a distantly related subfamily also forms functional homomultimeric channels. Although members of different K+ channel subfamilies do not coassemble, coexpression of the amino-terminal deletion mutants of hKv1.4 and Kv2.1 resulted in the formation of functional hybrid channels. These results demonstrate that the amino-terminal region of mammalian K+ channels subserves two functions. It provides a recognition site necessary for hetero- but not homomultimeric channel assembly within a subfamily and prevents coassembly between subfamilies.
Lee
T E
TE
University of Chicago, Department of Neurology, Illinois 60637.
Philipson
L H
LH
Kuznetsov
A
A
Nelson
D J
DJ
D000818:Animals; D001483:Base Sequence; D055592:Biophysical Phenomena; D001703:Biophysics; D017931:DNA Primers / Q000235:genetics; D004330:Drosophila / Q000235:genetics; D005260:Female; D007700:Kinetics; D008564:Membrane Potentials; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011487:Protein Conformation; D017384:Sequence Deletion; D014981:Xenopus
D017931:DNA Primers; D015221:Potassium Channels