The F-plasmid TraI protein contains three functional domains required for conjugative DNA strand transfer.
The F-plasmid-encoded TraI protein, also known as DNA helicase I, is a bifunctional protein required for conjugative DNA transfer. The enzyme catalyzes two distinct but functionally related reactions required for the DNA processing events associated with conjugation: the site- and strand-specific transesterification (relaxase) reaction that provides the nick required to initiate strand transfer and a processive 5'-to-3' helicase reaction that provides the motive force for strand transfer. Previous studies have identified the relaxase domain, which encompasses the first approximately 310 amino acids of the protein. The helicase-associated motifs lie between amino acids 990 and 1450. The function of the region between amino acids 310 and 990 and the region from amino acid 1450 to the C-terminal end is unknown. A protein lacking the C-terminal 252 amino acids (TraIDelta252) was constructed and shown to have essentially wild-type levels of transesterase and helicase activity. In addition, the protein was capable of a functional interaction with other components of the minimal relaxosome. However, TraIDelta252 was not able to support conjugative DNA transfer in genetic complementation experiments. We conclude that TraIDelta252 lacks an essential C-terminal domain that is required for DNA transfer. We speculate this domain may be involved in essential protein-protein interactions with other components of the DNA transfer machinery.
Matson
Steven W
SW
Department of Biology, CB#3280, Coker Hall, University of North Carolina, Chapel Hill, NC 27599-3280, USA. smatson@bio.unc.edu
Ragonese
Heather
H
D001692:Biological Transport; D003227:Conjugation, Genetic; D004247:DNA / Q000378:metabolism*; D004265:DNA Helicases / Q000235:genetics* / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D029968:Escherichia coli Proteins; D005144:F Factor / Q000235:genetics* / Q000502:physiology; D018014:Gene Transfer Techniques; D005816:Genetic Complementation Test; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion
D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D004247:DNA; C027093:TraI protein, E coli; D004265:DNA Helicases