'''F1-Gramicidin A in Sodium Dodecyl Sulfate Micelles (NMR)'''
===F1-Gramicidin A 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).
The line below this paragraph, {{ABSTRACT_PUBMED_12578352}}, adds the Publication Abstract to the page
(as it appears on PubMed at http://www.pubmed.gov), where 12578352 is the PubMed ID number.
-->
{{ABSTRACT_PUBMED_12578352}}
==About this Structure==
==About this Structure==
Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NT5 OCA].
Full experimental information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1NT5 OCA].
==Reference==
==Reference==
Line 30:
Line 34:
[[Category: Sds micelle]]
[[Category: Sds micelle]]
[[Category: Single-stranded helical dimer]]
[[Category: Single-stranded helical dimer]]
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 02:56:57 2008''
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 23:59:24 2008''
Revision as of 23:59, 28 July 2008
This article has been automatically seeded. Changes to this page should pertain to the PDB entry only and not to the protein or biomolecule in general.
Full experimental information is available from OCA.
ReferenceReference
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
