Characterization of Coxiella burnetii pyrB

The C. burnetii pyrB gene was cloned on a 7-kbp EcoR I fragment. DNA sequence analysis, enzyme assays, and amino acid homologies with E. coli and B. subtilis pyrB gene products suggest that (i) C. burnetii ATCase exists as a trimer, (ii) the microorganism may not synthesize a regulatory polypeptide, and (iii) pyrB may be part of an operon whose expression is under the control of an upstream promoter. The high degree of homology of the active site further suggests that a common mechanism of catalysis for ATCase exists between such diverse organisms as C. burnetii, E. coli, and B. subtilis.