SEQUENCE, CHROMOPHORE EXTRACTION AND 3-D MODEL OF THE PHOTOACTIVE YELLOW PROTEIN FROM RHODOBACTER-SPHAEROIDES

The photoactive yellow protein (pyp) gene has been isolated from Rhodo bacter sphaeroides by probing with a homologous PCR-product. A sequenc e analysis shows that this pyp gene encodes a 124 AA protein with 48% identity to the three known PYPs. Downstream from pyp, a number of adj acent open reading frames were identified, including a gene encoding a CoA-ligase homologue (pCL). This latter protein is proposed to be inv olved in PYP chromophore activation, required for attachment to the ap oprotein. We have demonstrated the presence of the chromophoric group, previously identified in PYP from Ectothiorhodospira halophila as tra ns 4-hydroxy cinnamic acid, in phototrophically cultured R. sphaeroide s cells by capillary zone electrophoresis. The basic structure of the chromophore binding pocket in PYP has been conserved, as shown by a 3D model of R. sphaeroides PYP, constructed by homology-based molecular modelling. In addition, this model shows that R. sphaeroides PYP conta ins a characteristic, positively charged patch. (C) 1998 Elsevier Scie nce B.V. All rights reserved.