{PDOC00463}
{PS00536; UBIQUITIN_ACTIVAT_1}
{PS00865; UBIQUITIN_ACTIVAT_2}
{BEGIN}
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* Ubiquitin-activating enzyme signatures *
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Ubiquitin-activating  enzyme  (E1 enzyme) [1,2] activates ubiquitin  by  first
adenylating with ATP its C-terminal  glycine  residue  and  thereafter linking
this residue to  the  side  chain  of  a  cysteine  residue in E1, yielding an
ubiquitin-E1   thiolester  and  free  AMP.   Later  the  ubiquitin  moiety  is
transferred to a  cysteine  residue on  one  of  the  many forms of ubiquitin-
conjugating enzymes (E2).

E1 is  a large monomeric protein of about 110 to 115 Kd (about 1000 residues).
In yeast  there are two forms (UBA1 and UBA2) [3], while in plants and mammals
multiple forms  exist  including  a  form  which is Y-linked in mouse and some
other mammals and which may be involved in spermatogenesis.

It has been shown [4] that  the  last of the five cysteines that are conserved
in the sequence of E1 from various species is the one that binds ubiquitin. We
have developed  two  patterns  specific for E1, the first pattern contains the
second of  the  five conserved cysteines while the second pattern includes the
active site cysteine.

-Consensus pattern: K-[AI]-[CL]-S-G-K-[FI]-x-[PQ]
-Sequences known to belong to this class detected by the pattern: ALL,  except
 for human UBE1L.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Consensus pattern: P-[LIVMG]-C-T-[LIVM]-[KRHA]-x-[FTNM]-P
                    [C is the active site residue]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

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

[ 1] Jentsch S., Seufert W., Hauser H.-P.
     "Genetic analysis of the ubiquitin system."
     Biochim. Biophys. Acta 1089:127-139(1991).
     PubMed=1647207
[ 2] Hershko A.
     "The ubiquitin pathway for protein degradation."
     Trends Biochem. Sci. 16:265-268(1991).
     PubMed=1656558
[ 3] Dohmen R.J., Stappen R., McGrath J.P., Forrova H., Kolarov J.,
     Goffeau A., Varshavsky A.
     "An essential yeast gene encoding a homolog of ubiquitin-activating
     enzyme."
     J. Biol. Chem. 270:18099-18109(1995).
     PubMed=7629121
[ 4] Hatfield P.M., Vierstra R.D.
     "Multiple forms of ubiquitin-activating enzyme E1 from wheat.
     Identification of an essential cysteine by in vitro mutagenesis."
     J. Biol. Chem. 267:14799-14803(1992).
     PubMed=1634524

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