The role of PBP1b along the cell envelope was supported by the findings that an E. However, PBP1b displays only mild localization at the cell septum and also localizes throughout the cell envelope indicative of PBP1b activity in both the elongasome and divisome ( Bertsche et al., 2006). coli, based on the interactions and localization patterns of PBP1a-PBP2 and PBP1b-PBP3, it was suggested that PBP1a and PBP2 function in the elongasome while PBP1b and PBP3 are specialized for PG biosynthesis in the divisome ( Randich & Brun, 2015).
The PBPs serve in different protein complexes and interact with different partners, which regulate their activity or localization. Bacillus subtilis has four class A PBPs and six class B PBPs ( Sauvage et al., 2008). The model organism, Escherichia coli possesses three class A PBPs (PBP1a, PBP1b and PBP1c) and two monofunctional class B PBPs (PBP2 and PBP3/FtsI) among over 36 enzymes required for PG polymerization. The number of PBPs varies among different bacterial species reflecting differences in bacterial lifestyles and modes of PG biosynthesis mechanisms. Class A PBPs contain a N-terminal transglycosylase domain of the GT51 family and a C-terminal transpeptidase domain, whereas Class B PBPs contain only a C-terminal transpeptidase domain ( Sauvage et al., 2008).
Class I is further comprised of two subclasses: Class A PBPs which are bifunctional, performing both transglycosylation and transpeptidation reactions and Class B PBPs which are monofunctional, performing only transpeptidation reactions. PBPs are functionally categorized into three classes: Class I PBPs that consist of High Molecular Weight (HMW) PBPs and Class II–III PBPs, which include Low Molecular Weight (LMW) PBPs ( Arora, Chawla, Malakar, Singh, & Nandicoori, 2018 Sauvage, Kerff, Terrak, Ayala, & Charlier, 2008). Kana, in Advances in Applied Microbiology, 2020 4 Penicillin binding proteins (PBPs) Herein, we describe a general protocol to label and detect the activity of individual PBPs in Streptococcus pneumoniae using our fluorescent β-lactone probes. We recently generated a library of fluorescent chemical probes containing a β-lactone scaffold that specifically targets the PBPs, enabling the visualization of their catalytic activity. Therefore, development of new methods for studying the roles of individual PBPs in cell wall synthesis is required. Existing techniques to study PBPs are not ideal because they do not directly visualize protein activity and can suffer from artifacts and perturbations of native PBP function. The apparent functional redundancy of the 4–18 PBPs that most eubacteria possess makes determination of their individual roles difficult. The importance of the PBPs has long been appreciated however, specific roles of individual family members in each bacterial strain, as well as their protein-protein interactions, are yet to be understood.
These proteins were discovered and named for their affinity to bind the β-lactam antibiotic penicillin. Penicillin-binding proteins (PBPs) are membrane-associated proteins involved in the biosynthesis of peptidoglycan (PG), the main component of bacterial cell walls. Carlson, in Methods in Enzymology, 2020 Abstract