The pyrH gene of Lactococcus lactis subsp cremoris encoding UMP kinase is transcribed as part of an operon including the frr1 gene encoding ribosomalrecycling factor 1

The pyrH gene of Lactococcus lactis subsp. cremoris MG1363, encoding UMP ki nase, has been sequenced and cloned. It encodes a polypeptide of 239 amino acid residues (deduced molecular weight of 25951), which was shown to compl ement a temperature sensitive pyrH mutation in Escherichia coli, thus estab lishing the ability of the encoded protein to synthesize UDP. The pyrH gene in L. lactis is flanked downstream by frr1 encoding ribosomal recycling fa ctor 1 and upstream by an open reading frame, orfA, of unknown function. Th e three genes were shown to constitute an operon transcribed in the directi on orfA-pyrH- from a promoter immediately in front of orfA. This operon bel ongs to an evolutionary highly conserved gene cluster, since the organizati on of pyrH on the chromosomal level in L. lactis shows a high resemblance t o that found in Bacillus subtilis as well as in Escherichia coli and severa l other prokaryotes (C) 2000 Elsevier Science B.V. All rights reserved.