1nt6
From Proteopedia
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F1-Gramicidin C In Sodium Dodecyl Sulfate Micelles (NMR)
Overview
To further investigate the effect of single amino acid substitution on the, structure and function of the gramicidin channel, an analogue of, gramicidin A (GA) has been synthesized in which Trp(15) is replaced by Gly, in the critical aqueous interface and cation binding region. The structure, of Gly(15)-GA incorporated into SDS micelles has been determined using a, combination of 2D-NMR spectroscopy and molecular modeling. Like the parent, GA, Gly(15)-GA forms a dimeric channel composed of two single-stranded, right-handed beta(6.3)-helices joined by hydrogen bonds between their, N-termini. The replacement of Trp(15) by Gly does not have a significant, effect on backbone structure or side chain conformations with the, exception of Trp(11) in which the indole ring is rotated away from the, channel axis. Measurement of the equilibrium binding constants and Delta G, for the binding of monovalent cations to GA and Gly(15)-GA channels, incorporated into PC vesicles using (205)Tl NMR spectroscopy shows that, monovalent cations bind much more weakly to the Gly(15)-GA channel, entrance than to GA channels. Utilizing the magnetization inversion, transfer NMR technique, the transport of Na(+) ions through GA and, Gly(15)-GA channels incorporated into PC/PG vesicles has been, investigated. The Gly(15) substitution produces an increase in the, activation enthalpy of transport and thus a significant decrease in the, transport rate of the Na(+) ion is observed. The single-channel, appearances show that the conducting channels have a single, well-defined, structure. Consistent with the NMR results, the single-channel, conductances are reduced by 30% and the lifetimes by 70%. It is concluded, that the decrease in cation binding, transport, and conductance in, Gly(15)-GA results from the removal of the Trp(15) dipole and, to a lesser, extent, the change in orientation of Trp(11).
About this Structure
1NT6 is a Protein complex structure of sequences from [1] with FOR as ligand. Full crystallographic information is available from OCA.
Reference
The structure, cation binding, transport, and conductance of Gly15-gramicidin A incorporated into SDS micelles and PC/PG vesicles., Sham SS, Shobana S, Townsley LE, Jordan JB, Fernandez JQ, Andersen OS, Greathouse DV, Hinton JF, Biochemistry. 2003 Feb 18;42(6):1401-9. PMID:12578352
Page seeded by OCA on Sat Nov 24 23:45:36 2007
