Assignment and secondary structure of the YadA membrane protein by solid-state MAS NMR

We report the complete solid-state MAS NMR resonance assignment of a medium-sized, trimeric membrane protein, YadA-M. The protein YadA (Yersinia adhesin A) is an important virulence factor of enteropathogenic Yersinia species (such as Yersinia enterocolitica and Yersinia pseudotuberculosis). YadA is localized on the bacterial cell surface and is involved in adhesion to host cells and tissues. It is anchored in the outer membrane by a transmembrane anchor domain (YadA-M). This domain hosts the so-called autotransporter function of YadA: it transports its own N-terminal domain through the outer membrane. The assignment is based on a dataset that consisted of several MAS NMR correlation spectra, recorded on a single, uniformly (13)C, (15)N- labelled microcrystalline preparation. Except for the single C-terminal residue and the mobile strep tag, we were able to completely assign YadA-M. From this, secondary structure elements were predicted, which, combined with several long-range interstrand restraints, yielded the architecture of the β-sheet.