Figure 10. 2D-NMR data recorded at high, low, and intermediate pH.

A uniform, stable, and monomeric tertiary structure is inferred by the 142 sharp, well-resolved peaks of main-chain amide resonances. The broader peaks at pH 7.4 suggest that AtraPBP1 exists as a heterogenous mixture of monomer, dimer, and multimer, as previously suggested for BmorPBP1 [36]. The NMR spectrum at intermediate pH is in agreement with a transition state with at least two conformations in equilibrium.