Model and anomalous signal for subunit A the MN-DEUT crystals (Table 1). The electron density (purple cage) represents anomalous signal for data collected at a wavelength of 1.8 Å and is contoured at 6 σ. The model is represented in stick format with carbon, oxygen, nitrogen, sulfur, and the metal (modeled as iron) colored tan, red, blue, cyan, and orange, respectively.