Referenced in: none

Automatically associated channels: Kir6.2 , Slo1

Title: Molecular basis of inward rectification: polyamine interaction sites located by combined channel and ligand mutagenesis.

Authors: Harley T Kurata, L Revell Phillips, Thierry Rose, Gildas Loussouarn, Stefan Herlitze, Hariolf Fritzenschaft, Decha Enkvetchakul, Colin G Nichols, Thomas Baukrowitz

Journal, date & volume: J. Gen. Physiol., 2004 Nov , 124, 541-54

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/15477380

Abstract
Polyamines cause inward rectification of (Kir) K+ channels, but the mechanism is controversial. We employed scanning mutagenesis of Kir6.2, and a structural series of blocking diamines, to combinatorially examine the role of both channel and blocker charges. We find that introduced glutamates at any pore-facing residue in the inner cavity, up to and including the entrance to the selectivity filter, can confer strong rectification. As these negative charges are moved higher (toward the selectivity filter), or lower (toward the cytoplasm), they preferentially enhance the potency of block by shorter, or longer, diamines, respectively. MTSEA+ modification of engineered cysteines in the inner cavity reduces rectification, but modification below the inner cavity slows spermine entry and exit, without changing steady-state rectification. The data provide a coherent explanation of classical strong rectification as the result of polyamine block in the inner cavity and selectivity filter.