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.
Department of Biochemistry and Molecular Biology, and Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637, USA.
Serdar
S
Uysal
Valeria
V
Vásquez
Valentina
V
Tereshko
Kaori
K
Esaki
Frederic A
FA
Fellouse
Sachdev S
SS
Sidhu
Shohei
S
Koide
Eduardo
E
Perozo
Anthony
A
Kossiakoff
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