Title: Three-dimensional structure of the KChIP1-Kv4.3 T1 complex reveals a cross-shaped octamer.

Authors: Marta Pioletti, Felix Findeisen, Greg L Hura, Daniel L Minor

Journal, date & volume: Nat. Struct. Mol. Biol., 2006 Nov , 13, 987-95

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/17057713

Abstract
Brain I(A) and cardiac I(to) currents arise from complexes containing Kv4 voltage-gated potassium channels and cytoplasmic calcium-sensor proteins (KChIPs). Here, we present X-ray crystallographic and small-angle X-ray scattering data that show that the KChIP1-Kv4.3 N-terminal cytoplasmic domain complex is a cross-shaped octamer bearing two principal interaction sites. Site 1 comprises interactions between a unique Kv4 channel N-terminal hydrophobic segment and a hydrophobic pocket formed by displacement of the KChIP H10 helix. Site 2 comprises interactions between a T1 assembly domain loop and the KChIP H2 helix. Functional and biochemical studies indicate that site 1 influences channel trafficking, whereas site 2 affects channel gating, and that calcium binding is intimately linked to KChIP folding and complex formation. Together, the data resolve how Kv4 channels and KChIPs interact and provide a framework for understanding how KChIPs modulate Kv4 function.