First glance on the three-dimensional structure of the photosynthetic reaction center from a herbicide-resistant Rhodopseudomonas viridis mutant.

A first model of the three-dimensional structure of the photosynthetic reaction center of the mutant T1 (SerL223----Ala, ArgL217----His) from Rhodopseudomonas viridis, resistant toward the triazine herbicide terbutryn (2-methylthio-4-ethylamino-6-t-butylamino-s-triazine), has been developed from X-ray data measured to a resolution of 2.5 A. The secondary quinone, QB, which in T1 binds better than in the wild type, is present in the crystals. Both substituted residues are clearly visible in the difference fourier map. The replacement of these two residues in the QB site causes only minor changes in the overall structure of the protein.