The desensitization gating of the MthK K+ channel is governed by its cytoplasmic amino terminus.
The RCK-containing MthK channel undergoes two inactivation processes: activation-coupled desensitization and acid-induced inactivation. The acid inactivation is mediated by the C-terminal RCK domain assembly. Here, we report that the desensitization gating is governed by a desensitization domain (DD) of the cytoplasmic N-terminal 17 residues. Deletion of DD completely removes the desensitization, and the process can be fully restored by a synthetic DD peptide added in trans. Mutagenesis analyses reveal a sequence-specific determinant for desensitization within the initial hydrophobic segment of DD. Proton nuclear magnetic resonance ((1)H NMR) spectroscopy analyses with synthetic peptides and isolated RCK show interactions between the two terminal domains. Additionally, we show that deletion of DD does not affect the acid-induced inactivation, indicating that the two inactivation processes are mutually independent. Our results demonstrate that the short N-terminal DD of MthK functions as a complete moveable module responsible for the desensitization. Its interaction with the C-terminal RCK domain may play a role in the gating process.
Kuo
Mario Meng-Chiang
MM
Structural Biology Laboratory, The Salk Institute, La Jolla, California, United States of America.
Maslennikov
Innokentiy
I
Molden
Brent
B
Choe
Senyon
S
D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002850:Chromatography, Gel; D003593:Cytoplasm / Q000378:metabolism; D004594:Electrophysiology; D004926:Escherichia coli / Q000378:metabolism / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015221:Potassium Channels / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D013104:Spheroplasts / Q000378:metabolism / Q000502:physiology
D019843:Archaeal Proteins; D010455:Peptides; D015221:Potassium Channels