ThevirBoperon of theAgrobacterium tumefaciensvirulence regulon has sequence similarities to B, Cand D open reading frames downstream of the pertussis toxin-operon and to the DNA transfer-operons of broad-host-range conjugative plasmids

The 28.6 kDa virulence regulon of te pTiC58 plasmid is comprised of six major operons (1), of which the virB operon is required for the transfer of the T-DNA from the resident Ti plasmid in Agrobacterium tumefaciens to plant cells.A growing body of indirect evidence suggests tat this operon encodes proteins that may simulate a bacterial conjugative transfer A PTortB IPLKDLRASLPRLAFMAAC .........TLLS5ATLPDLAO.