PROSITE documentation PDOC51287
Large T-antigen (T-ag) origin-binding domain (OBD) profile


The group of polyomaviruses is formed by the homonymous murine virus (Py) as well as other representative members such as the simian virus 40 (SV40) and the human BK and JC viruses [1]. Their large T antigen (T-ag) protein binds to and activates DNA replication from the origine of DNA replication (ori). Insofar as is known, the T-ag binds to the origin first as a monomer to its pentanucleotide recognition element. The monomers are then thought to assemble into hexamers and double hexamers, which constitute the form that is active in initiation of DNA replication. When bound to the ori, T-ag double hexamers encircle DNA [2]. T-ag is a multidomain protein that contains an N-terminal J domain (see <PDOC00553>), a central origin-binding domain (OBD), and a C-terminal superfamily 3 helicase domain (see <PDOC51206>) [3].

The overall fold of the ~130-residue T-ag OBD can be described as a central five-stranded antiparallel β-sheet flanked by two α-helices on one side and one α-helix and one 3(10)-helix on the other (see <PDB:1TBD>). Both faces of the central β-sheet are largely hydrophobic and are protected from solvent by the helices, thus forming two hydrophobic cores [4]. The T-ag OBD molecules are arranged as a spiral with a left-handed twist having six T-ag OBD's per turn. The spiral surrounds a central channel, the inner wall of which consists of α helices [4].

The profile we developed covers the entire T-ag OBD domain.

Last update:

November 2007 / Profile revised.


Technical section

PROSITE method (with tools and information) covered by this documentation:

T_AG_OBD, PS51287; Large T-antigen (T-ag) origin-binding domain (OBD) profile  (MATRIX)


1AuthorsIacoangeli A. Melucci-Vigo G. Risuleo G. Santi E.
TitleRole of mouse polyomavirus late region in the control of viral DNA replication: a review.
SourceBiochimie 77:780-786(1995).
PubMed ID8824775

2AuthorsBochkareva E. Martynowski D. Seitova A. Bochkarev A.
TitleStructure of the origin-binding domain of simian virus 40 large T antigen bound to DNA.
SourceEMBO J. 25:5961-5969(2006).
PubMed ID17139255

3AuthorsMeinke G. Bullock P.A. Bohm A.
TitleCrystal structure of the simian virus 40 large T-antigen origin-binding domain.
SourceJ. Virol. 80:4304-4312(2006).
PubMed ID16611889

4AuthorsLuo X. Sanford D.G. Bullock P.A. Bachovchin W.W.
TitleSolution structure of the origin DNA-binding domain of SV40 T-antigen.
SourceNat. Struct. Biol. 3:1034-1039(1996).
PubMed ID8946857

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