Influence of NaCl and pH on lysostaphin catalytic activity, cell binding, and bacteriolytic activity

Peptidoglycan-degrading enzymes are a group of proteins intensively studied as novel antibacterials, with some of them having reached pre-clinical and clinical stages of research. Many peptidoglycan-degrading enzymes have modular organization and consist of a catalytic and a cell wall binding domain. This property has been exploited in enzyme engineering efforts, and many new peptidoglycan-degrading enzymes were generated through domain exchange. However, rational combination of domains from different enzymes is still challenging since relative contribution of every domain to the cumulative bacteriolytic activity is not yet clearly understood. In this work, we investigated the influence of ionic strength and pH on the catalytic efficiency and cell binding of peptidoglycan-degrading enzyme lysostaphin and how this influence is reflected in the lysostaphin bacteriolytic activity. Contrary to generally accepted view, lysostaphin domains are not completely independent and their combination within one protein leads to increased bacteriolytic activity with increasing NaCl concentration, despite both catalysis and cell binding being inhibited by NaCl. This effect is likely mediated by changes in conformation of bacterial cell wall peptidoglycan rather than the physical inter-domain interaction.

Automated summary

Peptidoglycan-degrading enzymes are intensively studied as potential antibacterials, and their modular organization has been used to generate new enzymes through domain exchange. However, the contribution of different domains to bacteriolytic activity is still unclear. This study investigates the influence of ionic strength and pH on the catalytic efficiency and cell binding of lysostaphin, and finds that the combination of domains within lysostaphin leads to increased bacteriolytic activity with increasing NaCl concentration, despite inhibition of catalysis and cell binding by NaCl. This effect is likely mediated by changes in the conformation of bacterial cell wall peptidoglycan.