Crystal structure of full-length KcsA in its closed conformation.
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 A, as well as that of its isolated C-terminal domain at 2.6 A. The structure of the full-length KcsA-Fab complex reveals a well-defined, 4-helix bundle that projects approximately 70 A toward the cytoplasm. This bundle promotes a approximately 15 degree 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.
Uysal
Serdar
S
Department of Biochemistry and Molecular Biology, and Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
Vásquez
Valeria
V
Tereshko
Valentina
V
Esaki
Kaori
K
Fellouse
Frederic A
FA
Sidhu
Sachdev S
SS
Koide
Shohei
S
Perozo
Eduardo
E
Kossiakoff
Anthony
A
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D019151:Peptide Library; D015221:Potassium Channels / Q000737:chemistry*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D048170:Streptomyces lividans / Q000737:chemistry*
D001426:Bacterial Proteins; D007140:Immunoglobulin Fab Fragments; D019151:Peptide Library; D015221:Potassium Channels; C107790:prokaryotic potassium channel