The pathway for the biosynthesis of the bacterial cell wall is one of the most prolific antibiotic targets, exemplified by the widespread use of β-lactam antibiotics. Despite this, our structural understanding of class A penicillin binding proteins, which perform the last two steps in this pathway, is incomplete due to the inherent difficulty in their crystallization and the complexity of their substrates.
Fig: CryoEM structure of apo E. coli PBP1b: A Reconstruction of apo PBP1b at 3.28 Å resolution with GTase (glycosyltransferase), TPase (transpeptidase) and UB2H (putative activator binding) domains labelled. B Refined structure of apo PBP1b in ribbon representation and rainbow colouring from N to C terminus (blue to red).
Here, we determine the near atomic resolution structure of the 83 kDa class A PBP from Escherichia coli, PBP1b, using cryogenic electron microscopy and a styrene maleic acid anhydride membrane mimetic. PBP1b, in its apo form, is seen to exhibit a distinct conformation in comparison to Moenomycin-bound crystal structures. The work herein paves the way for the use of cryoEM in structure-guided antibiotic development for this notoriously difficult to crystalize class of proteins and their complex substrates.
Caveney, N.A., Workman, S.D., Yan, R. et al. CryoEM structure of the antibacterial target PBP1b at 3.3 Å resolution. Nat Commun 12, 2775 (2021). https://doi.org/10.1038/s41467-021-23063-6