Acute isolates of Coxiella burnetii possess a 36-kbp plasmid termed QpH1. DNA hybridizations show that QpH1 contains approximately 6-kbp region of DNA which is not present in the QpRS plasmid from chronic isolates. This QpH1-specific region of DNA contains the contiguous EcoRI fragments G, E, and D. The GED region was found to possess seven open reading frames (ORF's) coding for proteins ranging from 5.5 to 42.3 kDa in molecular mass when subcloned and expressed in vitro. Summing the predicted ORF's accounts for 95% of the GED coding potential. E. coli expression produced a stable 42.3-kDa protein from the pHIN19 subclone of GED. The ORF of the 42.3-kDa protein, termed cbhE', has been localized on GED by both in vitro transcription/translation and DNA sequencing. The cbhE' gene is estimated as 1142 bp in length with a putative promoter region of TCAACT (-35)-N16-TAAAAT (-10)-N14-AGAAGGA (Shine-Dalgarno)-N10-ATG.