Trichlorination of a Teicoplanin-Type Glycopeptide Antibiotic by the Halogenase StaI Evades Resistance

Abstract

Glycopeptide antibiotics (GPAs) include clinically important drugs used for the treatment of infections caused by Gram-positive pathogens. These antibiotics are specialized metabolites produced by several genera of actinomycete bacteria. While many GPAs are highly chemically modified, A47934 is a relatively unadorned GPA lacking sugar or acyl modifications, common to other members of the class, but which is chlorinated at three distinct sites. The biosynthesis of A47934 is encoded by a 68-kb gene cluster in Streptomyces toyocaensis NRRL 15009. The cluster includes all necessary genes for the synthesis of A47934, including two predicted halogenase genes, staI and staK. In this study, we report that only one of the halogenase genes, staI, is necessary and essential for A47934 biosynthesis. Chlorination of the A47934 scaffold is important for antibiotic activity, as assessed by binding affinity for the target N-acyl-d-Ala-d-Ala. Surprisingly, chlorination is also vital to avoid activation of enterococcal and Streptomyces VanB-type GPA resistance through induction of resistance genes. Phenotypic assays showed stronger induction of GPA resistance by the dechlorinated compared to the chlorinated GPA. Correspondingly, the relative expression of the enterococcal vanA resistance gene was shown to be increased by the dechlorinated compared to the chlorinated compound. These results provide insight into the biosynthesis of GPAs and the biological function of GPA chlorination for this medically important class of antibiotic.

Newest perspectives of glycopeptide antibiotics: biosynthetic cascades, novel derivatives, and new appealing antimicrobial applications

“…For example, dechlorinated vancomycin showed a decrease in antibacterial activity (Wadzinski et al 2016 ). Similarly, the halogenation of A47934 is not only necessary for antimicrobial activity but also for avoiding the induction of resistance mechanisms in some pathogens (Yim et al 2018 ). In contrast, the antimicrobial activity of dechlorinated A40926 is similar to that of A40926 (Beltrametti et al 2003 ).…”

“…If there exist two halogenases in the BGCs, three or four chlorinations will be installed in the GPA structure. As an exception, StaI encoding only one halogenase in the sta cluster of A47934 presents three halogenations at different moieties of amino acids on the A47934 scaffold (Yim et al 2018 ). In another specific case, atypical GPA complestatin contains six chlorine atoms derived from three different amino acid monomers of 1,3-dichloro-Hpg, 3,5-dichloro-Hpg, and 3,5-dichloro-hydroxybenzoylformate catalyzed by nonheme metal-free halogenase ComH (Chiu et al 2001 ).…”