A Structural Model of the Urease Activation Complex Derived from Ion Mobility-Mass Spectrometry and Integrative Modeling

The synthesis of active Klebsiella aerogenes urease via an 18-subunit enzyme apoprotein-accessory protein pre-activation complex has been well studied biochemically, but thus far this complex has remained refractory to direct structural characterization. Using ion mobility-mass spectrometry, we characterized several protein complexes between the core urease apoprotein and its accessory proteins, including the 610-kDa (UreABC)(3)(UreDFG)(3) complex. Using our recently developed computational modeling workflow, we generated ensembles of putative (UreABC)(3)(UreDFG)(3) species consistent with experimental restraints and characterized the structural ambiguity present in these models. By integrating structural information from previous studies, we increased the resolution of the ion mobility-mass spectrometry-derived models substantially, and we observe a discrete population of structures consistent with all of the available data for this complex.