Fig. 2.

Structure of αTSR. (A) CS αTSR showing layer residues and conserved flap fastening residues. (B) Layers of the TSR fold. Dashed boxes indicate layers lost in the αTSR. Dashed blue lines indicate π-cation and salt bridge interactions retained in αTSR, adapted from ref. 7. (C) Thrombospondin-1 TSR domain 1 (7) superimposed on the αTSR domain in A, Right and separated horizontally. Trp layers are colored orange and stacking layers are labeled by residue type. (D) Hydrophobic core of the αTSR domain. Conserved hydrophobic sidechains (with the exception of I346, in which many species have arginine or lysine sidechains) and their interactions are shown. A portion of the structure is omitted for clarity. (E) Transparent surface representation of αTSR with conserved hydrophobic pocket residues and their surface representation shaded orange. (F) Fitting of the crystal structure of αTSR to the final SWAXS envelope, shown as a transparent surface. The αTSR crystal structure is shown in cartoon in green, except the N-terminal YVEF is in orange. The YVEF sequence may be flexible in solution, because it is not included in the SWAXS envelope. Arrows indicate an observed indent on the SWAXS model corresponding to the approximate location of the hydrophobic pocket in the crystal structure. (G) Scattering curve calculated from the crystal structure and excluding the YVEF sequence (black) is overlaid to the raw experimental SWAXS scattering data for Pichia αTSR (red) and HEK293T αTSR (cyan). (H) Heparin-sepharose affinity assay of Pichia αTSR (red) and CS (black). Each construct was passed over a HiTrap heparin-sepharose column at a flow rate of 0.2 mL/min in 10 mM Tris pH 7.4 buffer and washed with a sodium chloride gradient (brown) over 40 column volumes.