FIGURE 3.

A sulfane modification on Cys¹²³ and a thiosulfate molecule in the active site of TsdA crystallized in the presence of tetrathionate. A, residual log likelihood gradient maps in data collected at λ = 1.4 Å after modeling the contribution of the iron atom. The maps, contoured at 3σ (gold), reveal density around the sulfur atoms in the active site. The peak heights correlate well with the thermal mobility and occupancies of the atoms. B, simulated annealing omit map, contoured at 3σ (green), calculated following exclusion of the two sulfur atoms within the cysteine S-sulfane moiety at the active site. C, simulated annealing omit map, contoured at 3σ (green), calculated following exclusion of both the bound thiosulfate molecule (modeled at 46% occupancy) and the water molecule that occupies the same location when the thiosulfate molecule is not present (54% occupancy).