Figure 2.

Fit of the atomic model to the map, contoured at 1.5 σ with atoms color-coded: carbon, green; nitrogen, blue; oxygen, red; and hydrogen; grey. (A) Tyr₄₈₅-Arg₄₈₆: bulges are apparent for all aliphatic and guanidinyl hydrogens and for the tyrosine hydroxyl; (B) Asn₅₂₀-Pro₅₂₁: the tetrahedral shape of the sp³ carbons define the pucker of this proline which is clearly in cis configuration; (C) His₃₆₀: the map is suggestive that there is a hydrogen at N_δ, and that the N_ε is predominantly deprotonated; (D) Tyr₂₈₃: the aromatic hydrogens are clearly visible, as is the hydroxyl, oriented for hydrogen bond donation to a solvent water that bridges to the carboxylate of Asp₂₈₅.