FIG. 2.

Gene organization of the Dtr regions of the transfer systems from RP4 and pTiC58. The black-filled arrows represent genes coding for the coupling proteins of the three transfer systems. (A) tra locus of the Ti plasmid tra system. Locations of genes within the two tra operons, as well as the oriT sequence, are indicated by the large arrows. The flagstaff represents the site of the Tn3HoHo1 insertion located in traG of the mutant Ti plasmid pDCKI41. The diagonally hatched bar represents the EcoRI fragment from pTiC58 containing traG cloned in pDCE20. The small arrow represents the location and direction of transcription of the native TraR-dependent promoter responsible for expression of the traCDG operon. (B) Tra1 core region of RP4. The locations of the essential Dtr genes and the oriT are shown by large arrows. The diagonally hatched bar depicts the fragment containing the traG gene cloned in pBS141. The arrow represents the Tac promoter, provided by the vector, that drives expression of the gene. (C) virD operon of the Ti plasmid. The five genes of the virD operon are shown by the large arrows. The diagonally hatched bar depicts the fragment containing the virD4 gene cloned in pHL142. The arrow represents the lac promoter, provided by the vector, that drives expression of the gene.