Crystal structure of full-length KcsA in its closed conformation
Abstract
KcsA is a proton-activated, voltage-modulated K+ channel that has served as the archetype pore domain in the Kv channel superfamily. Here, we have used synthetic antigen-binding fragments (Fabs) as crystallographic chaperones to determine the structure of full-length KcsA at 3.8 å, as well as that of its isolated C-terminal domain at 2.6 å. The structure of the full-length KcsA-Fab complex reveals a well-defined, 4-helix bundle that projects ≈70 å toward the cytoplasm. This bundle promotes a ≈15° bending in the inner bundle gate, tightening its diameter and shifting the narrowest point 2 turns of helix below. Functional analysis of the full-length KcsA-Fab complex suggests that the C-terminal bundle remains whole during gating. We suggest that this structure likely represents the physiologically relevant closed conformation of KcsA.
- Publication:
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Proceedings of the National Academy of Science
- Pub Date:
- April 2009
- DOI:
- 10.1073/pnas.0810663106
- Bibcode:
- 2009PNAS..106.6644U
- Keywords:
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- Biological Sciences:Biophysics and Computational Biology