Structure of the inactivating gate from the Shaker voltage gated K+ channel analyzed by NMR spectroscopy.

Rapid inactivation of voltage-gated K+ (Kv) channels is mediated by an N-terminal domain (inactivating ball domain) which blocks the open channel from the cytoplasmic side. Inactivating ball domains of various Kv channels are also biologically active when synthesized separately and added as a peptide to the solution. Synthetic inactivating ball domains from different Kv channels with hardly any sequence homology mediate quite similar effects even on unrelated Kv channel subtypes whose inactivation domain has been deleted. The solution structure of the inactivating ball peptide from Shaker (Sh-P22) was analyzed with NMR spectroscopy. The NMR data indicate a non-random structure in an aqueous environment. However, while other inactivating ball peptides showed well-defined three-dimensional structures under these conditions, Sh-P22 does not have a unique, compactly folded structure in solution.