Fig. 2: Structure of best-resolved STA class.

a Map and fitted MDFF model of class 12, which refined to the highest resolution (8.1 Å). Shown are top and cut-away views. Large and small subunits are colored blue and orange, respectively. b Alignment between two large subunits and two small subunits of class 12 MDFF model and PDB 1GK8. The MDFF model is colored as follows: the top and bottom large subunits are colored light and dark blue, respectively; the small subunits are colored orange, and key active site segments are colored dark red. Key segments include the large subunit loop 6 (aa 331-338), C-terminus (aa 461-475), loop 64-68, and the N-terminus (aa 7–21). Corresponding chains from PDB 1GK8 are colored grey. The 2-carboxyarabinitol-1,5-bisphosphate (2CABP) inhibitor from 1GK8, which marks the position of the active site, is shown in black atomic view. c Comparison of active site conformations. The conformational changes in these residues correlate with the Rubisco activity state. The MDFF model (dark red) is compared to PDB 1GK8 (grey, middle panel) and PDB 1EJ7 (cyan, bottom panel), which represent closed and open conformations, respectively. A better match is found for the closed state. The 2CABP inhibitor from 1GK8 is shown in black atomic view in all panels for reference.