{PDOC00950}
{PS01236; PDXT_SNO_1}
{PS51130; PDXT_SNO_2}
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* PdxT/SNO family signature and profile *
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The term  vitamin  B6 is used to refer collectively to the compound pyridoxine
and its  vitameric  forms,  pyridoxal,  pyridoxamine, and their phosphorylated
derivatives. Vitamin  B6  is  required by all organisms and plays an essential
role as   a  co-factor  for  enzymatic  reactions.  Plants,  fungi,  bacteria,
archaebacteria, and  protists  synthetize  vitamin B6. Animals and some highly
specialized obligate  pathogens  obtain  it  nutritionally. Vitamin B6 has two
distinct biosynthetic  pathways,  which  do  not  coexist in any organism. The
pdxA/pdxJ pathway,  that  has  been  extensively  characterized in Escherichia
coli, is  found  in  the  gamma  subdivision  of  the proteobacteria. A second
pathway of  vitamin  B6 synthesis involving the pdxS/SNZ (see <PDOC00949>) and
pdxT/SNO protein  families,  which are completely unrelated in sequence to the
pdxA/pdxJ proteins,  is  found in plants, fungi, protists, archaebacteria, and
most bacteria.

PdxS/SNZ and  pdxT/SNO  proteins  form  a  complex which serves as a glutamine
amidotransferase to supply ammonia as a source of the ring nitrogen of vitamin
B6 [1].  PdxT/SNO  and  pdxS/SNZ appear to encode respectively the glutaminase
subunit, which  produces  ammonia  from  glutamine,  and the synthase subunit,
which combines  ammonia  with  five-  and  three-carbon  phosphosugars to form
vitamin B6 [2].

The pdxT/SNO  family  belongs  to  the  triad glutamine aminotransferase fold,
characterized by  a  conserved  Cys-His-Glu  active  site [3]. Two regions are
highly conserved across all taxa, the PGGEST motif and the FHPE(LT) motif [4].
PdxT/SNO proteins  are  an alpha/beta three-layer sandwich containing a seven-
stranded twisted  mixed  parallel beta-sheet flanked by a six alpha-helices on
the N-terminal  stretch  of  the  sheet, four on one side and two on the other
(see <PDB:1R9G>) [3].

Some proteins belonging to the pdxT/SNO family are listed below:

 - Bacillus subtilis glutamine amidotransferase subunit pdxT (EC 2.6.-.-).
 - Haemophilus    influenzae    glutamine    amidotransferase   subunit   pdxT
   (EC 2.6.-.-).
 - Methanococcus    jannaschii   glutamine   amidotransferase   subunit   pdxT
   (EC 2.6.-.-).
 - Yeast probable glutamine amidotransferase SNO1 (EC 2.6.-.-).
 - Yeast probable glutamine amidotransferase SNO2 (EC 2.6.-.-).
 - Yeast probable glutamine amidotransferase SNO3 (EC 2.6.-.-).

These are hydrophilic proteins of about 19 to 25 Kd.

The pattern  we  developed for the pdxT/SNO family covers the PGGEST motif. We
also developed a profile for the pdxT/SNO family.

-Consensus pattern: [GARVS]-[LVI]-[ILAV]-[LIVF]-P-G-G-E-S-[TS]-[STAV]
-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: April 2006 / Pattern revised.

[ 1] Dong Y.-X., Sueda S., Nikawa J.-I., Kondo H.
     "Characterization of the products of the genes SNO1 and SNZ1 involved
     in pyridoxine synthesis in Saccharomyces cerevisiae."
     Eur. J. Biochem. 271:745-752(2004).
     PubMed=14764090
[ 2] Belitsky B.R.
     "Physical and enzymological interaction of Bacillus subtilis proteins
     required for de novo pyridoxal 5'-phosphate biosynthesis."
     J. Bacteriol. 186:1191-1196(2004).
     PubMed=14762015
[ 3] Bauer J.A., Bennett E.M., Begley T.P., Ealick S.E.
     "Three-dimensional structure of YaaE from Bacillus subtilis, a
     glutaminase implicated in pyridoxal-5'-phosphate biosynthesis."
     J. Biol. Chem. 279:2704-2711(2004).
     PubMed=14585832; DOI=10.1074/jbc.M310311200
[ 4] Ehrenshaft M., Daub M.E.
     "Isolation of PDX2, a second novel gene in the pyridoxine biosynthesis
     pathway of eukaryotes, archaebacteria, and a subset of eubacteria."
     J. Bacteriol. 183:3383-3390(2001).
     PubMed=11344146; DOI=10.1128/JB.183.11.3383-3390.2001

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