RESUMO
Strictosidine synthase is a central enzyme involved in the biosynthesis of almost all plant monoterpenoid indole alkaloids. Strictosidine synthase from Rauvolfia serpentina was heterologously expressed in Escherichia coli. Crystals of the purified recombinant enzyme have been obtained by the hanging-drop technique at 303 K with potassium sodium tartrate tetrahydrate as precipitant. The crystals belong to the space group R3 with cell dimensions of a=b=150.3 A and c=122.4 A. Under cryoconditions (120 K), the crystals diffract to about 2.95 A.
Assuntos
Carbono-Nitrogênio Liases/química , Rauwolfia/enzimologia , Sequência de Bases , Carbono-Nitrogênio Liases/genética , Carbono-Nitrogênio Liases/isolamento & purificação , Carbono-Nitrogênio Liases/metabolismo , Cristalografia por Raios X , DNA de Plantas/genética , Escherichia coli/genética , Rauwolfia/genética , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/isolamento & purificaçãoRESUMO
X-ray structures of the wild-type reaction centre from Rhodobacter sphaeroides have been determined to a resolution of 1.87 A in the neutral (dark) state and to 2.06 A in the charge-separated (light-excited) state. Whereas the overall protein structures of both states are rather similar, the domain around the secondary quinone shows significant shifts. The quinone molecule itself is observed at two different positions. In the neutral state, 55% of the quinone is located distally and 45% proximally to the cytoplasmic side. After excitation by light, however, at least 90% of the quinone is found at the proximal position. Results presented by Stowell et al. (1997) are confirmed, but the quality of crystallographic data has been improved. We compare the data with the structure of the mutant RC L 209 PY that keeps the Q(B) molecule in the proximal position even in the charge-neutral state.
