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Solution NMR studies of the integral membrane proteins OmpX and OmpA from Escherichia coli
Author(s) -
Fernández César,
Hilty Christian,
Bonjour Sophie,
Adeishvili Koba,
Pervushin Konstantin,
Wüthrich Kurt
Publication year - 2001
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)02742-9
Subject(s) - micelle , membrane protein , integral membrane protein , nuclear magnetic resonance spectroscopy , chemistry , membrane , bacterial outer membrane , relaxation (psychology) , escherichia coli , biophysics , crystallography , nuclear magnetic resonance , biochemistry , aqueous solution , stereochemistry , biology , physics , neuroscience , gene
Membrane proteins are usually solubilized in polar solvents by incorporation into micelles. Even for small membrane proteins these mixed micelles have rather large molecular masses, typically beyond 50 000 Da. The NMR technique TROSY (transverse relaxation‐optimized spectroscopy) has been developed for studies of structures of this size in solution. In this paper, strategies for the use of TROSY‐based NMR experiments with membrane proteins are discussed and illustrated with results obtained with the Escherichia coli integral membrane proteins OmpX and OmpA in mixed micelles with the detergent dihexanoylphosphatidylcholine (DHPC). For OmpX, complete sequence‐specific NMR assignments have been obtained for the polypeptide backbone. The 13 C chemical shifts and nuclear Overhauser effect data then resulted in the identification of the regular secondary structure elements of OmpX/DHPC in solution, and in the collection of an input of conformational constraints for the computation of the global fold of the protein. For OmpA, the NMR assignments are so far limited to about 80% of the polypeptide chain, indicating different dynamic properties of the reconstituted OmpA β‐barrel from those of OmpX. Overall, the present data demonstrate that relaxation‐optimized NMR techniques open novel avenues for studies of structure, function and dynamics of integral membrane proteins.