Figure 2: Structures of NpSRII active site.
From: New Insights on Signal Propagation by Sensory Rhodopsin II/Transducer Complex

(a) Structural differences between NpSRII ground state in I212121 space group (yellow) and in P21212 space group (green) and (b) between NpSRII M state in I212121 space group (yellow) and in P21212 space group (green).