Structural stability of E. coli trigger factor studied by synchrotron small-angle X-ray scattering

Solution small-angle X-ray scattering (SAXS) is an effective technique for quantitatively measuring the compactness and shape of proteins. We use SAXS to study the structural characteristics and unfolding transitions induced by urea for full length Escherichia coli trigger factor (TF) and a series of truncation mutants, obtaining and comparing the radiuses of gyration (Rg), the distance-distribution function (P(r) function) and integrated intensity of TF variants in native and unfolding states. The C-terminal 72-residue truncated mutant TF360 exhibited dramatic structural differences and reduced stability compared with the whole TF molecule, while the N-domain truncated mutant MC maintained its compact structure with reduced stability. These results indicate that the C-terminal region of TF plays an important role in the structural and conformational stabilities of the TF molecule, while the N-domain is relatively independent.