Specific targeting and killing of Gram-negative pathogens with an engineered phage lytic enzyme

90 Virulence Volume 4 Issue 1 Phage lytic enzymes have potential as new inroads toward novel antibiotics. Until now this approach has only been promising for Grampositive bacteria because in Gram-negatives the target of lytic action is protected by an outer envelope. Information gleaned from the structural studies of two plague proteins— pesticin and FyuA—allowed us to engineer a “hybrid” protein to address this problem. This hybrid consisted of T4 phage lysozyme linked to a FyuA targeting domain and was capable of killing Gram-negative cells. This work therefore presents a proof of principle that phage lytic enzymes can be engineered to cross the outer envelope. Furthermore, hybrid engineering handed us a tool for the mechanistic investigation of TonB mediated membrane transport. This commentary describes our recent efforts to test the efficacy of the hybrid in a mouse infection model and the directions this work might take in the future. In an age of rising antibiotic resistance humanity desperately needs to investigate new paths to antimicrobial chemotherapy. There are now several reports that show that lytic enzymes isolated from phages may work well as therapeutic agents against diseases caused by Gram-positive bacteria (Fischetti, Trends Microbiol 2005). Yet there is a problem in applying the same strategy to Gramnegative pathogens. The target of the toxic action of the lytic enzymes is a structural layer known as peptidoglycan which in Grampositive bacteria is exposed but in Gramnegative organisms is sequestered beneath a protective outer membrane where the lytic enzyme cannot reach it. Unexpectedly we found a way of addressing this problem by using X-ray crystallography to study a system of two interacting proteins from the plague bacterium (Lukacik et al., Proc Natl Acad Sci U S A 2012). One of these proteins was a bacterial toxin called Virulence News & Views