Fig. 6: Inter-protomer allosteric regulation in response to peptide binding.

a PneKC sample catalyzing sustained PneA modification that was used for cryo-EM imaging that led to the identification of two distinct conformations that both show ligand bound only in one protomer. b Density map of conformation 1 with one protomer showing density for GTP (purple/red) but not the other protomer (orange). c Density map of conformation 2 with one protomer showing density for both GTP and PneA (purple/red/magenta) while the other protomer again shows no density for ligands (orange). d Superimposition of the two protomers within each conformation. Both protomers exhibit a relaxed conformation in the PneKC pre-binding state (RMSD: 1.06 Å) and a tense conformation in the LP-bound state (RMSD: 1.09 Å). e Superimposition of pre-binding PneKC (gray) with LP-bound PneKC (purple/coral) with focus on one side of the cyclase ___domain, showing an overall contraction of 10.6 Å induced by PneA binding as measured by the movement of cyclase ___domain residue Leu645. f Superimposition of the GTP-bound protomer of the pre-binding state with the ligand-bound protomer of the LP-bound state focusing on the cyclase ___domain. The movement of residue Gln127 reveals a contraction by 6.6 Å. g Surface view of the ligand-free PneKC protomer from the Pre-binding (gray) and the LP-bound (orange) states, showing an allosterically induced contraction of the primary groove.