SMALL-ANGLE X-RAY SOLUTION SCATTERING STUDY ON THE DIMERIZATION OF THE FKBP25MEM FROM LEGIONELLA-PNEUMOPHILA

The dimerization of the FK506-binding peptidyl-prolyl cis/trans-isomer ase (PPIase) FKBP25mem (Mip (macrophage infectivity potentiator) prote in) from Legionella pneumophila was studied by small-angle X-ray solut ion scattering. A value of 44 kDa, independent on the protein concentr ation between 2 and 13 mg/ml, confirming that FKBP25mem is a dimer was found for the molecular mass of the protein. The radius of gyration o f the protein is 3.3 nm and the Pored volume 87 nm(3). A model of the shape of FKBP25mem was evaluated from the scattering curve. Each monom er consists of a proximal and a peripheral domain, which are perpendic ular to each other, The envelope of the crystallographic model of huma n FKBP12 fits well into the peripheral domain. The contact regions bet ween the two monomers in the dimeric protein are probably located betw een the N-terminal parts of the monomers.