title: Mass spectrometry defines the C-terminal dimerization domain and enables modeling of the structure of full-length OmpA.
abstract: The transmembrane domain of the outer membrane protein A (OmpA) from Escherichia coli is an excellent model for structural and folding studies of β-barrel membrane proteins. However, full-length OmpA resists crystallographic efforts, and the link between its function and tertiary structure remains controversial. Here we use site-directed mutagenesis and mass spectrometry of different constructs of OmpA, released in the gas phase from detergent micelles, to define the minimal region encompassing the C-terminal dimer interface. Combining knowledge of the location of the dimeric interface with molecular modeling and ion mobility data allows us to propose a low-resolution model for the full-length OmpA dimer. Our model of the dimer is in remarkable agreement with experimental ion mobility data, with none of the unfolding or collapse observed for full-length monomeric OmpA, implying that dimer formation stabilizes the overall structure and prevents collapse of the flexible linker that connects the two domains.
authors.affiliation: Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK.
authors.forename: Julien
authors.initials: J
authors.lastname: Marcoux
authors.affiliation: Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK.
authors.forename: Argyris
authors.initials: A
authors.lastname: Politis
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Dennis
authors.initials: D
authors.lastname: Rinehart
authors.affiliation: Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK.
authors.forename: David P
authors.initials: DP
authors.lastname: Marshall
authors.affiliation: Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK.
authors.forename: Mark I
authors.initials: MI
authors.lastname: Wallace
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.
authors.forename: Lukas K
authors.initials: LK
authors.lastname: Tamm
authors.affiliation: Chemistry Research Laboratory, University of Oxford, Oxford OX1 3TA, UK. Electronic address: carol.robinson@chem.ox.ac.uk.
authors.forename: Carol V
authors.initials: CV
authors.lastname: Robinson
mesh_terms: D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013058:Mass Spectrometry; D008823:Micelles; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary
chemical_list: D001425:Bacterial Outer Membrane Proteins; D008823:Micelles; C078167:OMPA outer membrane proteins
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