{PDOC01033}
{PS01330; PABS_1}
{PS51006; PABS_2}
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* Polyamine biosynthesis (PABS) domain signature and profile *
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The nearly  ubiquitous  polyamines  (putrescine,  spermidine and spermine) are
polycationic mediators   of   cell  proliferation  and  differentiation  whose
functions likely  provide both stability and neutralization for nucleic acids.
The following  polyamine  biosynthetic  enzymes  are  evolutionary related and
contain a polyamine biosynthesis (PABS) domain [1]:

 - Spermidine  synthase  (EC 2.5.1.16) (putrescine aminopropyltransferase). It
   catalyzes the last step in the biosynthesis of spermidine from arginine and
   methionine; the conversion of putrescine to spermidine using decarboxylated
   S-adenosylmethionine as the cofactor.
 - Spermine  synthase  (EC  2.5.1.22)  (spermidine aminopropyltransferase). It
   converts spermidine into spermine using decarboxylated S-adenosylmethionine
   as the cofactor.
 - Putrescine  N-methyltransferase  (EC  2.1.1.53). It catalyzes a step in the
   biosynthesis of  nicotine  in  plants;  the methylation of putrescine to N-
   methylputrescine using S-adenosylmethionine as the cofactor.

The PABS  domain  consists of two subdomains: an N-terminal subdomain composed
of six   beta-strands,   and   a   Rossmann-like   C-terminal  subdomain  (see
<PDB:1INL>). The  larger  C-terminal  catalytic  core  subdomain consists of a
seven-stranded beta-sheet  flanked  by  nine  alpha  helices.  This  subdomain
resembles a  topology  observed  in  a  number of nucleotide and dinucleotide-
binding enzymes,    and    in    S-adenosyl-L-methionine    (AdoMet)-dependent
methyltransferases (MTases) [2].

As a  signature  pattern, we selected a glycine-rich conserved region. We also
developed a  profile  that  spans  both  the  N-terminal  and  the  C-terminal
catalytic subdomains.

-Consensus pattern: [VAI]-[LAV]-[LIV](2)-G-G-G-x-[GC]-x(2)-[LIVA]-x-E
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Last update: October 2013 / Text and profile revised.

[ 1] Hashimoto T., Tamaki K., Suzuki K., Yamada Y.
     "Molecular cloning of plant spermidine synthases."
     Plant Cell Physiol. 39:73-79(1998).
     PubMed=9517003
[ 2] Korolev S., Ikeguchi Y., Skarina T., Beasley S., Arrowsmith C.,
     Edwards A., Joachimiak A., Pegg A.E., Savchenko A.
     "The crystal structure of spermidine synthase with a multisubstrate
     adduct inhibitor."
     Nat. Struct. Biol. 9:27-31(2002).
     PubMed=11731804; DOI=10.1038/nsb737

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