Differential activity of Rickettsia rickettsii ompAand ompBpromoter regions in a heterologous reporter gene system Policastro, Paul F. and Hackstadt, Ted,, 140, 2941-2949 (1994), doi = https://doi.org/10.1099/13500872-140-11-2941, publicationName = Microbiology Society, issn = 1350-0872, abstract= The outer membrane of the Gram-negative obligate intracellular parasite Rickettsia rickettsiicontains two large surface protein antigens with approximate molecular masses of 200 and 135 kDa termed rOmpA and rOmpB, respectively. rOmpB is the most abundant protein in the outer membrane, while rOmpA is a relatively minor constituent. Densitometry of intrinsically radiolabelled protein profiles from R. rickettsii-infected Vero cells indicated a molar ratio of approximately 1:9 between rOmpA and rOmpB. The putative promoter-5' untranslated regions (5' UTR) from their recently characterized genes (rompAand rompB) were placed in the promoter assay vector pKK232-8 to test whether these elements conserve aspects of differential expression in a heterologous host-reporter system. Primer extension analysis of RNA from Escherichia coliclones containing the constructs indicated that E. coliRNA polymerase faithfully utilizes rompAand rompBtranscription start sites identified previously in R. rickettsii.The rompBinsert directs 28-fold higher levels of chloramphenicol acetyl transferase activity than the rompAinsert., language=, type=