We investigated the role of epiQ in the biosynthesis of the lantibiotic epidermin. epiQ was essential for epidermin production. It was shown that EpiQ controls epidermin production by transcriptionally activating the epiA promoter, used for transcription of most of the epidermin biosynthetic genes. Additional copies of epiQ increased epidermin production in the epidermin-producing wild-type strain Staphylococcus epidermidis Tü3298. The epiA promoter region was characterized by primer extension analysis. Two inverted repeats, putative operator sites for EpiQ binding, are located upstream of the -35 region and one is localized downstream of the -10 region. Crude protein extracts from S. epidermidis Tü3298 and epiQ expressing Escherichia coli cells led to gel mobility shifts of a DNA fragment bearing the inverted repeat which is located immediately upstream of the -35 region. DNA fragments bearing the other two inverted repeats were not shifted. The epiQ gene product could be detected by overexpression in the E. coli T7 system using antiserum raised against synthetic peptides of EpiQ. Furthermore, EpiQ, like other DNA-binding proteins, was shown to bind strongly to heparin sepharose.