Transfer of rapid inactivation and sensitivity to the class III antiarrhythmic drug E-4031 from HERG to M-eag channels.
The gating behaviour and pharmacological sensitivity of HERG are remarkably different from the corresponding properties of M-eag, a structurally similar member of the Eag family of potassium channels. In contrast to HERG, M-eag exhibits no apparent inactivation and little rectification, and is insensitive to the class III antiarrhythmic drug E-4031. We generated chimeric channels of HERG and M-eag sequences and made point mutations to identify the region necessary for rapid inactivation in HERG. This region includes the P region and half of the S6 putative transmembrane domain, including sites not previously associated with inactivation and rectification in HERG. Transfer of a small segment of the HERG polypeptide to M-eag, consisting largely of the P region and part of the S6 transmembrane domain, is sufficient to confer rapid inactivation and E-4031 sensitivity to M-eag. This region differs from the corresponding region in M-eag by only fifteen residues. Previous hypotheses that rapid inactivation of HERG channels occurs by a C-type inactivation mechanism are supported by the parallel effects on rates of HERG inactivation and Shaker C-type inactivation by a series of mutations at two equivalent sites in the polypeptide sequences. In addition to sites homologous to those previously described for C-type inactivation in Shaker, inactivation in HERG involves a residue in the upstream P region not previously associated with C-type inactivation. Although this site is equivalent to one implicated in P-type inactivation in Kv2.1 channels, our data are most consistent with a single, C-type inactivation mechanism.
Department of Physiology, University of Wisconsin-Madison Medical School, Madison, WI 53706, USA.
I M
IM
Herzberg
M C
MC
Trudeau
G A
GA
Robertson
D000595:Amino Acid Sequence; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D027682:Cation Transport Proteins; D004268:DNA-Binding Proteins; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010880:Piperidines / Q000494:pharmacology*; D017354:Point Mutation; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000737:chemistry / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated; D011487:Protein Conformation; D011725:Pyridines / Q000494:pharmacology*; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG
D000889:Anti-Arrhythmia Agents; D027682:Cation Transport Proteins; D004268:DNA-Binding Proteins; C072312:ERG protein, human; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; C092509:KCNH6 protein, human; C496885:Kcnh1 protein, mouse; D010880:Piperidines; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011725:Pyridines; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG; C063968:E 4031