Galactose oxidase-glucan binding domain fusion proteins as targeting inhibitors of dental plaque bacteria

In order to inhibit the growth of bacteria present in the human oral cavity, a novel system which targets antimicrobial agents to dental plaque has been developed. This system involves a hybrid protein consisting of a peptide expressing the bactericidal properties of galactose oxidase (GAO) fused to the glucan binding domain (GBD) of the Streptococcus mutans glucosyltransferase-S enzyme. A gene encoding GAO from the fungus Fusarium sp. has been inserted into an Escherichia coli expression vector and fused to sequences encoding the GBD, which binds to the glucans synthesized by oral streptococci. Bacterial extracts expressing the hybrid protein were tested for their ability to target the GAO activity to an in vitro plaque model consisting of streptococcal cells bound to microtiter plate wells. The binding of the hybrid protein to the streptococcal cells through its GBD and the dependence of binding on the production of glucans by bacteria were demonstrated. Furthermore, killing of three different species of oral streptococci by bound hybrid protein in conjunction with the galactose-lactoperoxidase-iodide cytotoxic system has been demonstrated. These results suggest a novel strategy for controlling dental plaque formation as well as dental caries in humans.