Novel Electrophilic Scaffold for Imaging of Essential Penicillin-Binding Proteins in Streptococcus pneumoniae

Shabnam Sharifzadeh, Michael J. Boersma, Ozden Kocaoglu, Alireza Shokri, Clayton L. Brown, Joshua D. Shirley, Malcolm E. Winkler, Erin E. Carlson

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Peptidoglycan (PG) is a mesh-like heteropolymer made up of glycan chains cross-linked by short peptides and is the major scaffold of eubacterial cell walls, determining cell shape, size, and chaining. This structure, which is required for growth and survival, is located outside of the cytoplasmic membrane of bacterial cells, making it highly accessible to antibiotics. Penicillin-binding proteins (PBPs) are essential for construction of PG and perform transglycosylase activities to generate the glycan strands and transpeptidation to cross-link the appended peptides. The β-lactam antibiotics, which are among the most clinically effective antibiotics for the treatment of bacterial infections, inhibit PBP transpeptidation, ultimately leading to cell lysis. Despite this importance, the discrete functions of individual PBP homologues have been difficult to determine. These major gaps in understanding of PBP activation and macromolecular interactions largely result from a lack of tools to assess the functional state of specific PBPs in bacterial cells. We have identified β-lactones as a privileged scaffold for the generation of PBP-selective probes and utilized these compounds for imaging of the essential proteins, PBP2x and PBP2b, in Streptococcus pneumoniae. We demonstrated that while PBP2b activity is restricted to a ring surrounding the division sites, PBP2x activity is present both at the septal center and at the surrounding ring. These spatially separate regions of PBP2x activity could not be detected by previous activity-based approaches, which highlights a critical strength of our PBP-selective imaging strategy.

Original languageEnglish (US)
Pages (from-to)2849-2857
Number of pages9
JournalACS Chemical Biology
Volume12
Issue number11
DOIs
StatePublished - Nov 17 2017

Bibliographical note

Funding Information:
This work was supported by National Institutes of Health grants DP2OD008592 (E.E.C.), RO1GM113172 (M.E.W.), and RO1GM114315 (M.E.W.); a Pew Biomedical Scholar Award (E.E.C.); a Sloan Research Fellow Award (E.E.C.); and start-up funds from the University of Minnesota and Indiana University.

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