Validation of the single-stranded channel conformation of gramicidin A by solid-state NMR
AUTOR(ES)
Kovacs, F.
FONTE
The National Academy of Sciences
RESUMO
The monovalent cation selective channel formed by a dimer of the polypeptide gramicidin A has a single-stranded, right-handed helical motif with 6.5 residues per turn forming a 4-Å diameter pore. The structure has been refined to high resolution against 120 orientational constraints obtained from samples in a liquid-crystalline phase lipid bilayer. These structural constraints from solid-state NMR reflect the orientation of spin interaction tensors with respect to a unique molecular axis. Because these tensors are fixed in the molecular frame and because the samples are uniformly aligned with respect to the magnetic field of the NMR spectrometer, each constraint restricts the orientation of internuclear vectors with respect to the laboratory frame of reference. The structural motif of this channel has been validated, and the high-resolution structure has led to precise models for cation binding, cation selectivity, and cation conductance efficiency. The structure is consistent with the electrophysiological data and numerous biophysical studies. Contrary to a recent claim [Burkhart, B. M., Li, N., Langs, D. A., Pangborn, W. A. & Duax, W. L. (1998) Proc. Natl. Acad. Sci. USA 95, 12950–12955], the solid-state NMR constraints for gramicidin A in a lipid bilayer are not consistent with an x-ray crystallographic structure for gramicidin having a double-stranded, right-handed helix with 7.2 residues per turn.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=22161Documentos Relacionados
- Sodium ion binding in the gramicidin A channel. Solid-state NMR studies of the tryptophan residues.
- The binding site of sodium in the gramicidin A channel: comparison of molecular dynamics with solid-state NMR data.
- Solid-phase peptide synthesis and solid-state NMR spectroscopy of [Ala3-15N][Val1]gramicidin A.
- High-resolution solid-state NMR of quadrupolar nuclei
- High-speed magic angle spinning solid-state 1H nuclear magnetic resonance study of the conformation of gramicidin A in lipid bilayers.