R96 Q183 OH. N Q94 N 168RT203 R N R Gly67 N Q69 H148>N OH2 H2O R 146 R R s205 E222 7 Schematic diagram of the interactions between the chromophore and its surroundings in the S65T mutant. Possible hydrogen bonds are drawn as dashed lines K Brejc et al PNAS USA 1997, 94, 2306K.Brejc et.al PNAS USA 1997, 94, 2306