Structure Sucrose-phosphate synthase

rcsb pdb 2r66: crystal structure shows 2 rossman fold domains in sps. domain depicted in blue, domain b in red.

x-ray diffraction studies have revealed structure of halothermothrix orenii sps belongs gt-b fold family. other gt-b proteins, sps contains 2 rossman fold domains named domain , b domain. generally, structure of these domains similar, both contain central beta sheets surrounded alpha helices. however, domain consists of 8 parallel beta strands , 7 alpha helices while b domain contains 6 parallel beta strands , 9 alpha helices. these domains joined residue loops form substrate binding cleft, glucosyl group acceptor binds.

although h. orenii non-photosynthetic bacterium, various studies indicate structure of sps similar plant sps. first, antibodies high specificities plant sps target bacterial sps, indicating structure conserved enough antibody recognize enzyme antigen. furthermore, genomic studies reveal closely related plant homologues exhibit 54% sequence identities.