LoaP is a broadly conserved antiterminator protein that regulates antibiotic gene clusters in Bacillus amyloliquefaciens

A valuable resource available in the search for new natural products is the diverse microbial life that spans the planet. A large subset of these microorganisms synthesize complex specialized metabolites exhibiting biomedically important activities. A limiting step to the characterization of these compounds is an elucidation of the genetic regulatory mechanisms that oversee their production. Although proteins that control transcription initiation of specialized metabolite gene clusters have been identified, those affecting transcription elongation have not been broadly investigated. In this study, we analysed the phylogenetic distribution of the large, widespread NusG family of transcription elongation proteins and found that it includes a cohesive outgroup of paralogues (herein coined LoaP), which are often positioned adjacent or within gene clusters for specialized metabolites. We established Bacillus amyloliquefaciens LoaP as a paradigm for this protein subgroup and showed that it regulated the transcriptional readthrough of termination sites located within two different antibiotic biosynthesis operons. Both of these antibiotics have been implicated in plant-protective activities, demonstrating that LoaP controls an important regulon of specialized metabolite genes for this microorganism. These data therefore reveal transcription elongation as a point of regulatory control for specialized metabolite pathways and introduce a subgroup of NusG proteins for this purpose.