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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.

Original publication

DOI

10.1016/j.str.2014.03.004

Type

Journal article

Journal

Structure

Publication Date

06/05/2014

Volume

22

Pages

781 - 790

Keywords

Amino Acid Sequence, Bacterial Outer Membrane Proteins, Mass Spectrometry, Micelles, Models, Molecular, Molecular Sequence Data, Mutagenesis, Site-Directed, Protein Conformation, Protein Multimerization, Protein Structure, Tertiary