Extended Data Fig. 4: Substrate- and product-bound filaments.

a. Volume of PRPS1 filaments bound to phosphate/ATP (left), phosphate/ATP/R5P (middle), or phosphate/PRPP (right); protomers colored in blue or orange. b, top. Volume of one hexamer from a filament of PRPS1 bound to PRPP. Protomers are orange and blue, with the active site in yellow. b, bottom. Zoom in of active site indicated in (top), including the catalytic loop (dark blue), ATP (yellow), phosphate, magnesium, and coordinated waters. c–e. Volume showing the catalytic loop (dark blue or dark orange) and the ligands in the active site (yellow) for each of the filament structures presented in this work. f. Overlay of active sites shown in Main Text Fig. 3b–d and also including PRPS1 + ADP (light grey). g. Volume (top) describing location of slices (bottom) showing catalytic domains in two maps with well-resolved catalytic loops. h. Overlay of PRPS1 + ATP/R5P closed catalytic loop and key residues from the three PRPS structures from the PDB that also contain a closed catalytic loop (3MBI from Thermoplasma volcanium; 5T3O and 7PN0 from Thermus thermophilus). PRPS1 with ATP/R5P in blue, PDB models in grey. i. Overlay of PRPS1 with ATP/R5P (blue/orange) and 5T3O and 7PN0 from Thermus thermophilus (greys), showing the neighboring open and closed catalytic loops.