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PMID:2370849

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Citation

Kuldau, GA, De Vos, G, Owen, J, McCaffrey, G and Zambryski, P (1990) The virB operon of Agrobacterium tumefaciens pTiC58 encodes 11 open reading frames. Mol. Gen. Genet. 221:256-66

Abstract

Agrobacterium tumefaciens genetically transforms plant cells by transferring a copy of its T-DNA to the plant where it is integrated and stably maintained. In the presence of wounded plant cells this process is activated and mediated by the products of the vir genes which are grouped into six distinct loci. The largest is the virB locus spanning 9.5 kb. Transposon mutagenesis studies have shown that virB gene products are required for virulence but their functions remain largely unknown. To provide information relevant to understanding the function of VirB polypeptides, the nucleotide sequence of the virB operon from a nopaline plasmid, pTiC58, is presented here. Eleven open reading frames (ORFs) are predicted from this sequence. The predicted sizes of 10 of the 11 VirB polypeptides are verified by specific expression in Escherichia coli. Only the product of the smallest ORF potentially encoding a 5.8 kDa polypeptide has not been detected. The initiation of translation of five virB ORFs occurs at codons that overlap the termination codons of the ORF immediately upstream; thus, translational coupling may be an important mechanism for efficient translation of the large virB polycistronic mRNA. Based on hydropathy plot analysis nine of the virB ORFs encode proteins that may interact with membranes; these data support the earlier hypothesis that virB gene products may form a membrane pore or channel to mediate exit of the T-DNA copy (T-strands) from Agrobacterium into the plant cell. A comparison of the two published octopine virB sequences with the nopaline sequence presented here is made.

Links

PubMed

Keywords

Amino Acid Sequence; Arginine/analogs & derivatives; Arginine/genetics; Bacterial Proteins/genetics; Base Sequence; Electrophoresis, Polyacrylamide Gel; Molecular Sequence Data; Operon; Plasmids; Protein Biosynthesis; Restriction Mapping; Rhizobium/genetics; Virulence Factors

Significance

Annotations

Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status

AGRT5:VIRBA

part_of

GO:0043684: type IV secretion system complex

ECO:0000317: genomic context evidence used in manual assertion

C

Seeded From UniProt

Missing: with/from

AGRT5:VIRBA

involved_in

GO:0030255: protein secretion by the type IV secretion system

ECO:0000317: genomic context evidence used in manual assertion

P

Seeded From UniProt

Missing: with/from


See also

References

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