Regulates transcriptional attenuation of the pyrimidine nucleotide (pyr) operon in response to exogenous pyrimidines, probably by binding to specific sites on pyr mRNA. This probably disrupts an antiterminator hairpin in the RNA and favors formation of a downstream transcription terminator, leading to a reduced expression of downstream genes. Belongs to the purine/pyrimidine phosphoribosyltransferase family. PyrR subfamily. Unlike for B.subtilis, the PyrR protein of L.lactis was shown not to encode UPRTase activity.