Transcriptional repressor for the nicCDEFTP and nicXR operons, encoding the lower aerobic nicotinate degradation pathway. Acts under non-induced conditions: repression of the nicCDEFTP and nicXR operons becomes alleviated in presence of 6-hydroxynicotinate (6HNA). Cofactor degradation; nicotinate degradation [regulation]. Expressed both in the presence and in the absence of the 6-hydroxynicotinate (6HNA) inducer. Delayed growth when using nicotinate as sole carbon and energy source, growth is faster in the presence of 6HNA when compared with that of the wild-type strain.