Knowledge-based approach to tackle antimicrobial resistance

Integrons are highly efficient gene recruitment platforms and are found as part of mobile genetic elements such as plasmids. They are therefore a major force to be reckoned with in the fight against AR. The project ICADIGE (The integron cassette dynamics and the integrase gene expression) has investigated the molecular dynamics of the integron and the enzyme responsible for integration of further genes, integrase.

The researchers worked with the genes and their products that allow insertion of more cassettes. These included the int1 gene that codes for an enzyme that belongs to the integrase family and an attC sequence that flanks cassettes and enables other cassettes to be integrated at the attI site.

To explore the evolutionary possibilities of the integrase protein, the scientists recoded the int1 gene into two alternative yet synonymous genes. Mutations were then subjected to directed evolution experiments. Able to identify frequencies of the different mutations, the researchers also characterised structural data on constraints of the reaction.

By looking at the evolution of the three genes in parallel, ICADIGE has induced elements of convergent and parallel evolution, epistatic interactions where alleles of the mutations masked effects of others, and re-evolution of amino acid residues.

Understanding the elements of AR could lead to the development of molecules that will halt the recombination process that leads to production of new mutations for resistance. Key proteins in the process that have been isolated can be crystallised for further work on their part in AR.