Expression, refolding and crystallization of the OpcA invasin from Neisseria meningitidis

OpcA is an integral outer membrane from the Gram-negative pathogen Neisseri a meningitidis that plays a role in adhesion of meningococci to host cells. The protein was overexpressed in Escherichia coli in an insoluble form and a procedure developed for refolding by rapid dilution from denaturant into detergent solution. The refolded material was identical to native OpcA iso lated from meningococci, as judged by overall molecular weight, migration o n SDS-PAGE and reaction against monoclonal antibodies. Both native and reco mbinant OpcA crystallized under similar conditions to give an orthorhombic crystal form (P2(1)2(1)2), with unit-cell parameters a = 96.9, b = 46.3, c = 74.0 Angstrom. Complete data sets of reflections were collected from nati ve and refolded OpcA to 2.0 Angstrom resolution.