Blocker protection in the pore of a voltage-gated K+ channel and its structural implications.
The structure of the bacterial potassium channel KcsA has provided a framework for understanding the related voltage-gated potassium channels (Kv channels) that are used for signalling in neurons. Opening and closing of these Kv channels (gating) occurs at the intracellular entrance to the pore, and this is also the site at which many open channel blockers affect Kv channels. To learn more about the sites of blocker binding and about the structure of the open Kv channel, we investigated here the ability of blockers to protect against chemical modification of cysteines introduced at sites in transmembrane segment S6, which contributes to the intracellular entrance. Within the intracellular half of S6 we found an abrupt cessation of protection for both large and small blockers that is inconsistent with the narrow 'inner pore' seen in the KcsA structure. These and other results are most readily explained by supposing that the structure of Kv channels differs from that of the non-voltage-gated bacterial channel by the introduction of a sharp bend in the inner (S6) helices. This bend would occur at a Pro-X-Pro sequence that is highly conserved in Kv channels, near the site of activation gating.
del Camino
D
D
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Holmgren
M
M
Liu
Y
Y
Yellen
G
G
D001426:Bacterial Proteins; D003545:Cysteine; D006860:Hydrogen Bonding; D047908:Intracellular Signaling Peptides and Proteins; D015640:Ion Channel Gating; D008698:Mesylates / Q000494:pharmacology; D008958:Models, Molecular; D010455:Peptides / Q000378:metabolism / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D000644:Quaternary Ammonium Compounds / Q000378:metabolism / Q000494:pharmacology; D051637:Shaker Superfamily of Potassium Channels; D055672:Static Electricity; D019789:Tetraethylammonium / Q000378:metabolism / Q000494:pharmacology
D001426:Bacterial Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008698:Mesylates; D010455:Peptides; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D000644:Quaternary Ammonium Compounds; D051637:Shaker Superfamily of Potassium Channels; C107790:prokaryotic potassium channel; C076103:Shaker B inactivating peptide; C109153:(2-sulfonatoethyl)methanethiosulfonate; C109154:(2-(trimethylammonium)ethyl)methanethiosulfonate; D019789:Tetraethylammonium; C009405:tetrabutylammonium; D003545:Cysteine; D011188:Potassium