{PDOC00524}
{PS00603; TK_CELLULAR_TYPE}
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* Thymidine kinase cellular-type signature *
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Thymidine kinase (TK) (EC 2.7.1.21) is an ubiquitous enzyme that catalyzes the
ATP-dependent phosphorylation of thymidine.   A comparison of TK sequences has
shown [1,2,3] that there are two different families of TK.   One family groups
together TK from herpesviruses as well as cellular thymidylate kinases,  while
the second family currently consists of TK from the following sources:

 - Vertebrates.
 - Bacterial.
 - Bacteriophage T4.
 - Poxviruses.
 - African swine fever virus (ASF).

As a signature pattern  for  this family of TK we selected a  conserved region
which is located in the C-terminal section of these enzymes.

-Consensus pattern: [GA]-x(1,2)-[DE]-x-Y-x-[STAPV]-x-C-[NKR]-x-[CH]-[LIVMFYWH]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Note: Proteins belonging to this family  also contain a copy  of the ATP/GTP-
 binding motif 'A' (P-loop) in their N-terminal extremity (see <PDOC00017>).

-Last update: December 2004 / Pattern and text revised.

[ 1] Boyle D.B., Coupar B.E.H., Gibbs A.J., Seigman L.J., Both G.W.
     "Fowlpox virus thymidine kinase: nucleotide sequence and relationships
     to other thymidine kinases."
     Virology 156:355-365(1987).
     PubMed=3027984
[ 2] Blasco R., Lopez-Otin C., Munoz M., Bockamp E.-O., Simon-Mateo C.,
     Vinuela E.
     "Sequence and evolutionary relationships of African swine fever virus
     thymidine kinase."
     Virology 178:301-304(1990).
     PubMed=2389555
[ 3] Robertson G.R., Whalley J.M.
     "Evolution of the herpes thymidine kinase: identification and
     comparison of the equine herpesvirus 1 thymidine kinase gene reveals
     similarity to a cell-encoded thymidylate kinase."
     Nucleic Acids Res. 16:11303-11317(1988).
     PubMed=2849761

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