Figure 4.

TDP1 N-terminus adopts an open conformation upon protein dephosphorylation.A, SEC- SAXS-MALS chromatographs for TDP1, TDP1 with λ phosphatase, and TDP1_149–608. Solid lines represent the UV 280 nm (light blue) or SAXS signal (blue) in arbitrary units, while symbols represent molecular mass determined by MALS (cyan) and R_g values for the principal SEC peak (blue) versus elution time. SEC-SAXS-MALS results show that TDP1 is a monomer. B, normalized pair distribution [P(r)] functions of TDP1 and TDP1 with λ phosphatase matching theoretical P(r) functions of atomistic models (black) shown in panel C. Normalized P(r) functions of TDP1_149–608 matching theoretical P(r) functions of TDP1 crystal structure (PDB 1JY1). C, ensemble models of two conformers of TDP1 and λ phosphatase-treated TDP1 that were used to fit experimental SAXS curves shown in Figure S8 and P(r) functions shown in panel B.