The lytic enzymes that target Gram-positive bacteria nearly universally have a two-domain structure, with the N-terminal catalytic domain bound through a short linker to a cell wall binding domain. We have exploited this modularity in designing new enzyme systems.
We have exploited the extraordinary specificity of lytic enzyme cell wall binding domains (CBD) when coupled with silver nanoparticles to kill target bacteria (Figure 1) [Kim et al. ACS Appl. Mater. Interfaces 10, 13,317-13,324 (2018)]. As a relevant example, CBDBA (binding domain from Bacillus anthracis) selectively bound to B. anthracis in a mixture with B. subtilis, as well as in a mixture with Staphylococcus aureus. As a result, the nonselective antimicrobial silver was converted into a highly selective antimicrobial targeting organisms that are bound selectively by a specific CBD. This new biologically-assisted hybrid strategy, therefore, has the potential to provide selective decontamination of pathogenic bacteria with minimal impact on normal microflora.
The modular nature of cell lytic enzymes can be exploited through unique assemblies (Figure 2). Cell lytic enzymes consist of catalytic and cell wall binding domains, which can be swapped among those of other lytic enzymes to produce unnatural chimeric enzymes. We have shown that microbially-generated biotinylated catalytic domains (CD) and cell wall binding domains (CBD) from the bacteriocin lysostaphin (Lst) and a putative autolysin from Staphylococcus aureus (SA1) can be assembled with streptavidin to form chimeric lytic enzymes [Kim et al. Biomacromolecules 20, 4035-4043, 2019].