Probably regulates transcriptional attenuation of the pyrimidine nucleotide (pyr) operon in response to exogenous pyrimidines. In contrast to pyr attenuation in Bacillus, PyrR from Thermus could act as a translational repressor: the binding of PyrR at its proposed recognition site in the transcript would prevent initiation of translation of the leader peptide, resulting in terminator formation and reduced expression of downstream genes (By similarity). Also displays uracil phosphoribosyltransferase activity (By similarity). diphosphate + UMP = 5-phospho-alpha-D-ribose 1-diphosphate + uracil Belongs to the purine/pyrimidine phosphoribosyltransferase family. PyrR subfamily.