The pore region of the Kv1.2alpha subunit is an important component of recombinant Kv1.2 channel oxygen sensitivity.
Oxygen-sensitive K(+) channels are important elements in the cellular response to hypoxia. Although much progress has been made in identifying their molecular composition, the structural components associated to their O(2)-sensitivity are not yet understood. Recombinant Kv1.2 currents expressed in Xenopus oocytes are inhibited by a decrease in O(2) availability. On the contrary, heterologous Kv2.1 channels are O(2)-insensitive. To elucidate the protein segment responsible for the O(2)-sensitivity of Kv1.2 channels, we analyzed the response to anoxia of Kv1.2/Kv2.1 chimeric channels. Expression of chimeric Kv2.1 channels each containing the S4, the S1-S3 or the S6-COOH segments of Kv1.2 polypeptide resulted in a K(+) current insensitive to anoxia. In contrast, transferring the S5-S6 segment of Kv1.2 into Kv2.1 produced an O(2)-sensitive K(+) current. Finally, mutating a redox-sensitive methionine residue (M380) of Kv1.2 polypeptide did not affect O(2)-sensitivity. Thus, the pore and its surrounding regions of Kv1.2 polypeptide confer its hypoxic inhibition. This response is independent on the redox modulation of methionine residues in this protein segment.
Conforti
Laura
L
Division of Nephrology and Hypertension, Department of Internal Medicine, University of Cincinnati, 231 Albert Sabin Way, Cincinnati, OH 45267-0585, USA. Laura.Conforti@uc.edu
Takimoto
Koichi
K
Petrovic
Milan
M
Pongs
Olaf
O
Millhorn
David
D
D000595:Amino Acid Sequence; D000818:Animals; D004594:Electrophysiology; D000860:Hypoxia; D051663:Kv1.2 Potassium Channel; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D017354:Point Mutation; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000737:chemistry* / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D017434:Protein Structure, Tertiary; D018075:RNA, Complementary / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014981:Xenopus
D051663:Kv1.2 Potassium Channel; D010455:Peptides; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D018075:RNA, Complementary; D011994:Recombinant Proteins; D011188:Potassium; D010100:Oxygen