Figure 2: Crystal structure of Ssb.
(a) Domain architecture of Ssb (residue numbers are given for C. thermophilum; corresponding residues in S. cerevisiae are in brackets). Ssb comprises an NBD (shades of blue) and an SBD consisting SBDβ (purple) and SBDα (lid domain, brown). A conserved linker (DLLLLDV, green) connects the NBD to the SBD. (b) Crystal structure of Ssb in the open conformation (cartoon representation). Ssb is a canonical Hsp70 with the NBD (subdomains IA, IIA, IB and IIB in different shades of blue) contacting both the SBDβ and the SBDα. SBDα is fixed on the NBD (bound ATP shown in sticks) by an engineered disulfide bridge (shown as sticks, see Supplementary Fig. 4). (c) Surface representation of Ssb (left and middle panel) and DnaK (right panel; pdb code 4b9q (ref. 11)) coloured by residue conservation (left panel) or electrostatic surface potential (middle and right panel). Insets show a close-up view of conserved residues from Ssb-SBDα forming a positively charged surface patch absent in DnaK. Surface charge spans from −4 kT/e (deep red) to +4 kT/e (deep blue). Conservation surface mapping are as reported by ConSurf84 and spans from variable (cyan) to conserved (deep red). Figures were produced using PDB2PQR (refs 71, 72) and APBS (ref. 70) in PyMOL (ref. 68).
