Protein Domain : PdxT/SNO family, conserved site IPR021196

Type	Conserved_site
Description	The term vitamin B6 is used to refer collectively to the compound pyridoxine and its vitameric forms, pyridoxal, pyridoxamine, and their phosphorylatedderivatives. 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 specialised obligate pathogens obtain it nutritionally. Vitamin B6 has twodistinct biosynthetic pathways, which do not coexist in any organism. The pdxA/pdxJ pathway, that has been extensively characterised in Escherichiacoli, is found in the gamma subdivision of the proteobacteria. A second pathway of vitamin B6 synthesis involving the pdxS/SNZ andpdxT/SNO protein families, which are completely unrelated in sequence to the pdxA/pdxJ proteins, is found in plants, fungi, protists, archaebacteria, andmost 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 vitaminB6 [ ]. PdxT/SNO and pdxS/SNZ appear to encode respectively the glutaminasesubunit, which produces ammonia from glutamine, and the synthase subunit, which combines ammonia with five- and three-carbon phosphosugars to formvitamin B6 [ ].The pdxT/SNO family belongs to the triad glutamine aminotransferase fold,characterised by a conserved Cys-His-Glu active site [ ]. Two regions arehighly conserved across all taxa, the PGGEST motif and the FHPE(LT) motif [ ].PdxT/SNO proteins are an alpha/beta three-layer sandwich containing a seven- stranded twisted mixed parallel β-sheet flanked by a six α-helices onthe N-terminal stretch of the sheet, four on one side and two on the other [ ].Proteins belonging to the pdxT/SNO family include:Bacillus subtilis glutamine amidotransferase subunit pdxT Haemophilus influenzae glutamine amidotransferase subunit pdxT Methanococcus jannaschii glutamine amidotransferase subunit pdxTYeast probable glutamine amidotransferase SNO1Yeast probable glutamine amidotransferase SNO2Yeast probable glutamine amidotransferase SNO3These are hydrophilic proteins of about 19 to 25 Kd.This entry represents a conserved site containing the PGGEST motif.
Short Name	PdxT/SNO_CS