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National Institute of General Medical Sciences (NIGMS) and National Cancer Institute (NCI) of the National Institutes of Health (NIH)
 

A full-length potassium channel

Anthony Kossiakoff group (University of Chicago) and collaborators

 

The groups of Anthony Kossiakoff, Eduardo Perozo, and Shohei Koide at the University of Chicago determined the crystal structure of the full-length potassium channel, KcsA, in its closed conformation. The tetrameric, proton-activated, voltage-modulated K+ channel has provided the highest-resolution structures of ion channels to date. However, previous KcsA structures lacked a C-terminal domain (residues 125-160) that stabilizes the closed form of the channel. With the aid of synthetic Fabs, full-length KcsA was crystallized, revealing a 4-helix bundle extending about 70 Å into the cytoplasm. The bundle promotes a 15 degree bend in the inner bundle gate, tightening its diameter from about 4 Å to about 2.5 Å, and shifting the narrowest point by two helical turns into the membrane bilayer. The 4-helix bundle is proposed to remain intact during gating, and the structure to represent the physiologically relevant closed state of KcsA.

Figure: Influence of the C-terminal truncation on the conformation of the inner helix gate of KcsA. (A) Cα superposition of the high-resolution truncated KcsA structure (1K4C; red) with full-length KcsA (blue). Inset highlights the splaying out of the inner helix bundle gate between residues 110 and 115, resulting in a 15 degree outward tilting. (B) Radius profile of truncated (red) and full-length KcsA (blue).

 

Citation:
Uysal, S, Vasquez, V, Tereshko, V, Esaki, K, Fellouse, FA, Sidhu, SS, Koide, S, Perozo, E, Kossiakoff, A., Crystal structure of full-length KcsA in its closed conformation, Proc. Natl. Acad. Sci. USA 106 (16), 6644-6649 (2009). DOI: 10.1073/pnas.0810663106


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