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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 γ 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 α/β three-layer sandwich containing a seven-stranded twisted mixed parallel β-sheet flanked by a six α-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.

April 2006 / Pattern revised.

PROSITE methods (with tools and information) covered by this documentation:

PDXT_SNO_2, PS51130; PdxT/SNO family profile  (MATRIX)

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

• Domain architecture view of Swiss-Prot proteins matching PS51130 • Retrieve an alignment of Swiss-Prot true positive hits:   Clustal format, color, condensed view  / Clustal format, color  / Clustal format, plain text  / Fasta format • Retrieve the sequence logo from the alignment • Taxonomic tree view of all Swiss-Prot/TrEMBL entries matching PS51130 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS51130 • Scan Swiss-Prot/TrEMBL entries against PS51130 • view ligand binding statistics

Matching PDB structures: 1Q7R 1R9G 2ISS 2NV0 ... [ALL]

PDXT_SNO_1, PS01236; PdxT/SNO family family signature  (PATTERN)

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.

• Retrieve an alignment of Swiss-Prot true positive hits:   Clustal format, color, condensed view  / Clustal format, color  / Clustal format, plain text  / Fasta format • Retrieve the sequence logo from the alignment • Taxonomic tree view of all Swiss-Prot/TrEMBL entries matching PS01236 • Retrieve a list of all Swiss-Prot/TrEMBL entries matching PS01236 • Scan Swiss-Prot/TrEMBL entries against PS01236 • view ligand binding statistics

Matching PDB structures: 1Q7R 1R9G 2ISS 2NV0 ... [ALL]

1	Authors	Dong Y.-X., Sueda S., Nikawa J.-I., Kondo H.
	Title	Characterization of the products of the genes SNO1 and SNZ1 involved in pyridoxine synthesis in Saccharomyces cerevisiae.
	Source	Eur. J. Biochem. 271:745-752(2004).
	PubMed ID	14764090

2	Authors	Belitsky B.R.
	Title	Physical and enzymological interaction of Bacillus subtilis proteins required for de novo pyridoxal 5'-phosphate biosynthesis.
	Source	J. Bacteriol. 186:1191-1196(2004).
	PubMed ID	14762015

3	Authors	Bauer J.A., Bennett E.M., Begley T.P., Ealick S.E.
	Title	Three-dimensional structure of YaaE from Bacillus subtilis, a glutaminase implicated in pyridoxal-5'-phosphate biosynthesis.
	Source	J. Biol. Chem. 279:2704-2711(2004).
	PubMed ID	14585832
	DOI	10.1074/jbc.M310311200

4	Authors	Ehrenshaft M., Daub M.E.
	Title	Isolation of PDX2, a second novel gene in the pyridoxine biosynthesis pathway of eukaryotes, archaebacteria, and a subset of eubacteria.
	Source	J. Bacteriol. 183:3383-3390(2001).
	PubMed ID	11344146
	DOI	10.1128/JB.183.11.3383-3390.2001

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