Document Detail

NMR studies of a channel protein without membranes: structure and dynamics of water-solubilized KcsA.
MedLine Citation:
PMID:  18948596     Owner:  NLM     Status:  MEDLINE    
Structural studies of polytopic membrane proteins are often hampered by the vagaries of these proteins in membrane mimetic environments and by the difficulties in handling them with conventional techniques. Designing and creating water-soluble analogues with preserved native structures offer an attractive alternative. We report here solution NMR studies of WSK3, a water-soluble analogue of the potassium channel KcsA. The WSK3 NMR structure (PDB ID code 2K1E) resembles the KcsA crystal structures, validating the approach. By more stringent comparison criteria, however, the introduction of several charged residues aimed at improving water solubility seems to have led to the possible formations of a few salt bridges and hydrogen bonds not present in the native structure, resulting in slight differences in the structure of WSK3 relative to KcsA. NMR dynamics measurements show that WSK3 is highly flexible in the absence of a lipid environment. Reduced spectral density mapping and model-free analyses reveal dynamic characteristics consistent with an isotropically tumbling tetramer experiencing slow (nanosecond) motions with unusually low local ordering. An altered hydrogen-bond network near the selectivity filter and the pore helix, and the intrinsically dynamic nature of the selectivity filter, support the notion that this region is crucial for slow inactivation. Our results have implications not only for the design of water-soluble analogues of membrane proteins but also for our understanding of the basic determinants of intrinsic protein structure and dynamics.
Dejian Ma; Tommy S Tillman; Pei Tang; Eva Meirovitch; Roderic Eckenhoff; Anna Carnini; Yan Xu
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2008-10-23
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  105     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2008 Oct 
Date Detail:
Created Date:  2008-10-29     Completed Date:  2008-12-01     Revised Date:  2013-02-08    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  16537-42     Citation Subset:  IM    
Department of Anesthesiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA.
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MeSH Terms
Bacterial Proteins
Escherichia coli Proteins / chemistry*
Hydrogen Bonding
Magnetic Resonance Spectroscopy*
Models, Molecular*
Molecular Structure
Potassium Channels / chemistry*
Potassium Channels, Voltage-Gated
Grant Support
Reg. No./Substance:
0/Bacterial Proteins; 0/Escherichia coli Proteins; 0/KcsA protein, Streptomyces coelicolor; 0/Potassium Channels; 0/Potassium Channels, Voltage-Gated; 0/Solutions; 7732-18-5/Water

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