Cloning and characterization of a Kv1.5 delayed rectifier K+ channel from vascular and visceral smooth muscles.
We have cloned and characterized the expression of a Kv1.5 K+ channel (cKv1.5) from canine colonic smooth muscle. The amino acid sequence displayed a high level of identity to other K+ channels of the Kv1.5 class in the core region between transmembrane segments S1-S6; however, identity decreased to between 74 and 82% in the NH2 and COOH terminal segments, suggesting that cKv1.5 is a distinct isoform of the Kv1.5 class. Functional expression of cKv1.5 in oocytes demonstrated a channel highly selective for K+, which activates in a voltage-dependent manner on depolarization to membrane potentials positive to -40 mV. At room temperature the channel showed fast activation (time to half of peak current, 5.5 ms) and slow inactivation that was incomplete after 20-s depolarizations. Single channel analysis of the channel expressed in oocytes displayed a linear current-voltage curve and had a slope conductance of 9.8 +/- 1.1 pS. Northern blot analysis demonstrated differential expression of cKv1.5 in smooth muscles of the gastrointestinal tract and abundant expression in several vascular smooth muscles. We propose that cKv1.5 represents a component of the delayed rectifier current in both vascular and visceral smooth muscles.
Overturf
K E
KE
Department of Physiology, University of Nevada School of Medicine, Reno 89557.
Russell
S N
SN
Carl
A
A
Vogalis
F
F
Hart
P J
PJ
Hume
J R
JR
Sanders
K M
KM
Horowitz
B
B
D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004064:Digestive System / Q000378:metabolism*; D004285:Dogs; D004594:Electrophysiology; D005260:Female; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D014982:Xenopus laevis
D018076:DNA, Complementary; D015221:Potassium Channels; D004247:DNA