Characterisation of peptides designed against the omega loop of class A β-lactamases to reverse antimicrobial resistance in bacteria

Sarmistha Biswal

Abstract

Mycobacterial infections result in huge damage to public health and economy each year because of the alarming emergence of extensively drug-resistant strains of Mycobacterium tuberculosis (WHO, 2019). Mycobacteria have long known to be intrinsically resistant to β-lactam antibiotics. Β-lactamases are enzymes those protect bacterial cells by hydrolyzing β-lactam ring of antibiotics making them ineffective. Class-A β-lactamases have a conserved structural domain called omega loop (RLDRWETELNEAIPGDARD) participating in catalytic activity being a part of the drug-binding pocket of the enzyme. In this work we have attempted to design and characterize some peptides against the omega-loop of class A β-lactamases to reverse antimicrobial resistance in bacteria. Primarily, about 100 peptides were designed against the conserved sequence of omega-loop of class A β-lactamases. The peptides sequences were subjected to different bioinformatics tool and finally, 10 peptides were synthesized by Fmoc Solid-Phase Synthesis Peptide (SPPS) strategy (J.M. Palomo, 2014). Whole-cell phenotypic evaluations were done to ascertain the hydrolytic potential of pbad-blatem1 (class A β-lactamases) against different β-lactam antibiotics in presence of all the synthesized peptides in different bacteria (E. Coli CS109, Mycobacterium smegmatis and Mycobacterium tuberculosis H37Rv) and we observed a significant decreased level of hydrolytic activity of blatem1 in the presence of peptides. Thus, the study may explore the role of peptides in masking of omega-loop facilitating β-lactams to kill the bacteria.