Fig. 6.

The BbCuZnSOD disulfide subloop is stabilized by interactions with Try14 and loop I. (A) 2Fo-Fc electron density map contoured at 2σ showing opposing Tyr14 residues forming side-chain hydrophobic interactions (3.4 Å) at the BbCuZnSOD homodimer interface aligned with the same site on the human SOD1 surface (gray and dark gray). (B) 2Fo-Fc electron density map contoured at 2σ showing how the BbCuZnSOD disulfide subloop is stabilized by a hydrogen bond interaction with loop I Gln17. Both loops are longer than that found in human SOD1 (gray). (C) The BbCuZnSOD interface interaction network. Reciprocal and symmetric interactions described in (A) and (B) combine to stabilize disulfide subloops and the homodimer interface. Residues from opposing monomers are colored blue and gray with hydrogen bonds dashed black.