{PDOC51287}
{PS51287; T_AG_OBD}
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* Large T-antigen (T-ag) origin-binding domain (OBD) profile *
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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 beta-sheet flanked by two alpha-helices on one side
and one  alpha-helix  and  one 3(10)-helix on the other (see <PDB:1TBD>). Both
faces of the central beta-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 alpha helices [4].

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

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.
-Last update: November 2007 / Profile revised.

[ 1] Iacoangeli A., Melucci-Vigo G., Risuleo G., Santi E.
     "Role of mouse polyomavirus late region in the control of viral DNA
     replication: a review."
     Biochimie 77:780-786(1995).
     PubMed=8824775
[ 2] Bochkareva E., Martynowski D., Seitova A., Bochkarev A.
     "Structure of the origin-binding domain of simian virus 40 large T
     antigen bound to DNA."
     EMBO J. 25:5961-5969(2006).
     PubMed=17139255; DOI=10.1038/sj.emboj.7601452
[ 3] Meinke G., Bullock P.A., Bohm A.
     "Crystal structure of the simian virus 40 large T-antigen
     origin-binding domain."
     J. Virol. 80:4304-4312(2006).
     PubMed=16611889; DOI=10.1128/JVI.80.9.4304-4312.2006
[ 4] Luo X., Sanford D.G., Bullock P.A., Bachovchin W.W.
     "Solution structure of the origin DNA-binding domain of SV40
     T-antigen."
     Nat. Struct. Biol. 3:1034-1039(1996).
     PubMed=8946857

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