The 2.2 Å Crystal Structure of Hsp33 J. Vijayalakshmi, Matthew K. Mukhergee, Johannes Graumann, Ursula Jakob, Mark A. Saper  Structure  Volume 9, Issue 5, Pages 367-375 (May 2001) DOI: 10.1016/S0969-2126(01)00597-4

Figure 1 Sequence Comparison of Selected Hsp33 Homologs Hsp33 sequences from 18 different eubacterial species were aligned with Clustal W and analyzed with AMAS [21]. Sequence positions with AMAS conservation scores of seven or greater were considered “conserved” for the Hsp33 structure and are highlighted in green. Invariant residues are colored red. Six representative sequences from the complete alignment are shown. Red stars mark the four invariant cysteines. Sequence numbers are for E. coli Hsp33. Secondary structures (arrows for β strands and cylinders for α helices) were assigned with DSSP [22]. Strands β10 and β11 have β-like conformation but were not flagged as β strands by DSSP. The blue arrow indicates the site of proteolytic cleavage in the full-length mutant protein and the carboxy terminus of the truncated Hsp33. GenBank or NCBI microbial genome accession codes for Hsp33 homologs: Streptococcus mutans, UOKNOR_1309, contig89 (unfinished genome fragment); Staphylococcus aureus, Sanger_1280_3, contig3; Clostridium difficile, Sanger_1496 contig1019 (unfinished genome fragment); E. coli, P45803; Neisseria gonorrhoeae, OUACGT_485 (unfinished genome fragment); Pseudomonas aeruginosa, AAG08578 Structure 2001 9, 367-375DOI: (10.1016/S0969-2126(01)00597-4)

Figure 2 Structure of the Hsp33(1–255) Dimer (a–c) Side view of the dimer. (d–f) View of the dimer showing the 10-stranded intermolecular β sheet. The orientation was generated by rotating a, b, or c by ∼90° along the horizontal axis. (a and d) RIBBONS [23] representation of the secondary structure with the two subunits colored blue and orange. Strands β5, β4, β3, β6, and β7 form the five-stranded sheet that forms the intermolecular 10-strand β sheet referred to in the text. Strands β1, β2, β9, and β8 form the four-stranded β sheet. Note that α5, α6, α7, β10, and β11 comprise the domain that is swapped onto the other protomer. (b and e) Solvent contact surface with electrostatic potential. The electrostatic potential varies from −12→0→+12 and is encoded by a red→white→blue color ramp. Regions of nonpolar carbon atoms are depicted in yellow. White areas indicate regions that are polar but uncharged. The figure was prepared with GRASP [24] and POV4GRASP [25]. (c and f) CPK representation, with conserved side chains highlighted in green. The labeled residues from the other subunit are in an oblique font. The figure was prepared with Molecular Images software [26] Structure 2001 9, 367-375DOI: (10.1016/S0969-2126(01)00597-4)

Figure 3 Opening to the Buried Cavity and Dimer Interface Residues 1–178 (core domain) of the Hsp33(1–255) structure is rotated from Figure 2a by ∼90° along the vertical axis and rendered as CPK spheres [26]. Side chains defined as conserved in Figure 1 are colored green. Atoms that make contact within 4 Å of the other subunit are outlined in white Structure 2001 9, 367-375DOI: (10.1016/S0969-2126(01)00597-4)

Figure 4 The Glu150-Glu150 Intersubunit Hydrogen Bond Buried in the Dimer Interface The buried cavities are to the left and right of the Glu150 pair. The putative MES buffer molecule modeled into the electron density found in the cavities is colored in gray. Hydrogen bonds are depicted as small white spheres. The labeled residues from the other subunit are in oblique font. The figure was rendered with Molecular Images Software [26] Structure 2001 9, 367-375DOI: (10.1016/S0969-2126(01)00597-4)

Figure 5 Alpha-Carbon Backbone of Half of the Hsp33 Dimer Residues 1–178 from one subunit are in blue, and residues 179–234 from the other subunit are in orange. The figure was prepared with RIBBONS [23] Structure 2001 9, 367-375DOI: (10.1016/S0969-2126(01)00597-4)