Extended Data Fig. 5: RbCBM74 selects a double helical ligand geometry.

a. Overlay of RbCBM74 from Sas6T structure (PDB 7uww) in blue with RbCBM74 from BIg-RbCBM74-BIg co-crystal structure (PDB 7uwv) in deep teal. b. Loop from G374-G382 demonstrating that the unliganded loop (blue) occludes W373 but moves to allow access to W373 in the ligand-bound structure (deep teal). c. An extended view of the geometry of the G10 ligand. Intramolecular hydrogen bonds (3.6Å cutoff for ideal geometry and 3.2Å with minimal acceptable geometry) within and between G10 chains are shown in slate. Φ (O5-C1-O4′-C4′) and ψ (C1-O4′-C4′-C5′) angles of the Glc linkages in the G10 double helix ligand are labeled with G10A in magenta and G10B in grey. d. The geometry of the G10 ligand more closely resembles that of double helical B starch (cyan)⁴⁸ than single helical cycloamylose (yellow, 1c58)⁵⁰. Models were manually aligned in PyMOL to compare the angles, pitch, and period of the helical turns.