Small‐angle X‐ray solution scattering study on the dimerization of the FKBP25mem from Legionella pneumophila

Abstract
The dimerization of the FK506‐binding peptidyl‐prolyl cisltrans‐isomerase (PPIase) FKBP25mem (Mip (macrophage infectivity potentiator) protein) from Legionella pneumophila was studied by small‐angle X‐ray solution scattering. A value of 44 kDa, independent on the protein concentration 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 of the protein is 3.3 nm and the Porod volume 87 nm3. A model of the shape of FKBP25mem was evaluated from the scattering curve. Each monomer consists of a proximal and a peripheral domain, which are perpendicular to each other. The envelope of the crystallographic model of human FKBP12 fits well into the peripheral domain. The contact regions between the two monomers in the dimeric protein are probably located between the N‐terminal parts of the monomers.