The complete nucleotide sequence of the vir B locus, from the octopine Ti plasmid of Agrobacterium tumefaciens strain 15955, has been determined. In the large vir B-operon (9600 nucleotides) we... Show moreThe complete nucleotide sequence of the vir B locus, from the octopine Ti plasmid of Agrobacterium tumefaciens strain 15955, has been determined. In the large vir B-operon (9600 nucleotides) we have identified eleven open reading frames, designated vir B1 to vir B11. From DNA sequence analysis it is proposed that nearly all VirB products, i.e. VirB1 to VirB9, are secreted or membrane associated proteins. Interestingly, both a membrane protein (VirB4) and a potential cytoplasmic protein (VirB11) contain the consensus amino acid sequence of ATP-binding proteins. In view of the conjugative T-DNA transfer model, the VirB proteins are suggested to act at the bacterial surface and there play an important role in directing T-DNA transfer to plant cells. Show less
