Figure 5.

Crystal structure of tetrameric I99C β-tryptase mutant at 2.7 Å resolution. A, I99C β-tryptase mutant is shown in green and blue, with internal disulfides in yellow and the I99C disulfide in orange. Cysteine residues are shown as spheres for the disulfides; sulfur atoms are yellow for internal disulfides and orange for I99C disulfides. B, tetramer was rotated ∼90°; only one of the disulfide-locked dimers is shown. C, I99C protomer is superposed with one from the WT structure (1A0L), which is shown in beige. The catalytic triad residues are shown as sticks.