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Nonrandom structure in the urea-unfolded Escherichia coli outer membrane protein X (OmpX)

Tafer, Hakim and Hiller, Sebastian and Hilty, Christian and Fernández, César and Wüthrich, Kurt. (2004) Nonrandom structure in the urea-unfolded Escherichia coli outer membrane protein X (OmpX). Biochemistry, 43 (4). pp. 860-869.

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Official URL: http://edoc.unibas.ch/41060/

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Abstract

On the basis of sequence-specific resonance assignments for the complete polypeptide backbone and most of the amino acid side chains by heteronuclear nuclear magnetic resonance (NMR) spectroscopy, the urea-unfolded form of the outer membrane protein X (OmpX) from Escherichia coli has been structurally characterized. (1)H-(1)H nuclear Overhauser effects (NOEs), dispersion of the chemical shifts, amide proton chemical shift temperature coefficients, amide proton exchange rates, and (15)N[(1)H]-NOEs show that OmpX in 8 M urea at pH 6.5 is globally unfolded, but adopts local nonrandom conformations in the polypeptide segments of residues 73-82 and 137-145. For these two regions, numerous medium-range and longer-range NOEs were observed, which were used as the input for structure calculations of these polypeptide segments with the program DYANA. The segment 73-82 forms a quite regular helical structure, with only loosely constrained amino acid side chains. In the segment 137-145, the tryptophan residue 140 forms the core of a small hydrophobic cluster. Both nonrandom structures are present with an abundance of about 25% of the protein molecules. The sequence-specific NMR assignment and the physicochemical characterization of urea-denatured OmpX presented in this paper are currently used as a platform for investigations of the folding mechanism of this integral membrane protein.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Structural Biology & Biophysics > Structural Biology (Hiller)
UniBasel Contributors:Hiller Odermatt, Sebastian
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Chemical Society
ISSN:0006-2960
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
Identification Number:
Last Modified:07 Feb 2018 09:43
Deposited On:17 Aug 2016 07:03

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