Monomer Addition as a Mechanism of Forming Peptide Cross-Links in the Cell-Wall Peptidoglycan of Streptococcus faecalis ATCC 9790

AbstractTuberculosis is a deadly disease that requires a flexible arsenal of drugs to treat it. Although β-lactam antibiotics are rarely used to treat Mycobacterium tuberculosis (Mtb) infections today, the targets of these drugs are present in the bacterium. Moreover, the cell wall peptidoglycan of Mtb contains an abundance of unusual (3→3) cross-links. These cross-links are formed by enzymes called L,D-transpeptidases, which are susceptible to inhibition by the carbapenem class of antibiotics. We developed new small molecule probes to investigate the L,D-transpeptidases and other β-lactam drug targets in Mtb. We synthesized probes based on three classes of antibiotics, a monobactam, cephalosporin, and carbapenem. For the carbapenem, we synthesized a meropenem analogue conjugated to a far-red fluorophore. This probe was particularly useful in identifying active L,D-transpeptidases in protein gel-resolved lysates. Next we analyzed β-lactam targets in lysates from both hypoxic and actively-replicating cultures of Mtb. We identified numerous targets, including transpeptidases, carboxypeptidases, and the β-lactamase BlaC. Overall, we provide evidence that Mtb dynamically regulates the enzymes responsible for maintaining cell wall peptidoglycan and that meropenem is a good inhibitor of those enzymes.

Download Full-text

Effect of Staphylococcus aureus Cell-Wall Peptidoglycan on the Rat Myometrial Contractility Regulation by Adenylate Cyclase Signaling System

International Journal of Physiology and Pathophysiology ◽

10.1615/intjphyspathophys.v8.i1.70 ◽

2017 ◽

Vol 8 (1) ◽

pp. 65-76

Author(s):

Lilit S. Nasibyan ◽

Igor B. Philyppov

Keyword(s):

Staphylococcus Aureus ◽

Cell Wall ◽

Adenylate Cyclase ◽

Signaling System ◽

Cell Wall Peptidoglycan ◽

Myometrial Contractility ◽

Adenylate Cyclase Signaling System

Download Full-text

Bacterial Peptidoglycan Stapling with Functionalized D-Amino Acids

10.26434/chemrxiv.10248764.v1 ◽

2019 ◽

Author(s):

Sylvia L. Rivera ◽

Akbar Espaillat ◽

Arjun K. Aditham ◽

Peyton Shieh ◽

Chris Muriel-Mundo ◽

...

Keyword(s):

Cell Wall ◽

Clinical Success ◽

Bacterial Species ◽

Enzymatic Reaction ◽

Amino Acid Derivative ◽

Wall Structure ◽

Live Bacteria ◽

Cross Links ◽

Osmotic Lysis ◽

Bacterial Peptidoglycan

Transpeptidation reinforces the structure of cell wall peptidoglycan, an extracellular heteropolymer that protects bacteria from osmotic lysis. The clinical success of transpeptidase-inhibiting β-lactam antibiotics illustrates the essentiality of these cross-linkages for cell wall integrity, but the presence of multiple, seemingly redundant transpeptidases in many bacterial species makes it challenging to determine cross-link function precisely. Here we present a technique to covalently link peptide strands by chemical rather than enzymatic reaction. We employ bio-compatible click chemistry to induce triazole formation between azido- and alkynyl-D-alanine residues that are metabolically installed in the cell walls of Gram-positive and Gram-negative bacteria. Synthetic triazole cross-links can be visualized by substituting azido-D-alanine with azidocoumarin-D-alanine, an amino acid derivative that undergoes fluorescent enhancement upon reaction with terminal alkynes. Cell wall stapling protects the model bacterium Escherichia coli from β-lactam treatment. Chemical control of cell wall structure in live bacteria can provide functional insights that are orthogonal to those obtained by genetics.<br>

Download Full-text