title: A new arrangement of (beta/alpha)8 barrels in the synthase subunit of PLP synthase.
abstract: Pyridoxal 5'-phosphate (PLP, vitamin B6), a cofactor in many enzymatic reactions, has two distinct biosynthetic routes, which do not coexist in any organism. Two proteins, known as PdxS and PdxT, together form a PLP synthase in plants, fungi, archaea, and some eubacteria. PLP synthase is a heteromeric glutamine amidotransferase in which PdxT produces ammonia from glutamine and PdxS combines ammonia with five- and three-carbon phosphosugars to form PLP. In the 2.2-A crystal structure, PdxS is a cylindrical dodecamer of subunits having the classic (beta/alpha)8 barrel fold. PdxS subunits form two hexameric rings with the active sites positioned on the inside. The hexamer and dodecamer forms coexist in solution. A novel phosphate-binding site is suggested by bound sulfate. The sulfate and another bound molecule, methyl pentanediol, were used to model the substrate ribulose 5-phosphate, and to propose catalytic roles for residues in the active site. The distribution of conserved surfaces in the PdxS dodecamer was used to predict a docking site for the glutaminase partner, PdxT.
authors.affiliation: Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Jianghai
authors.initials: J
authors.lastname: Zhu
authors.forename: John W
authors.initials: JW
authors.lastname: Burgner
authors.forename: Etti
authors.initials: E
authors.lastname: Harms
authors.forename: Boris R
authors.initials: BR
authors.lastname: Belitsky
authors.forename: Janet L
authors.initials: JL
authors.lastname: Smith
mesh_terms: D000641:Ammonia / Q000737:chemistry; D001412:Bacillus subtilis / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D002384:Catalysis; D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000378:metabolism; D005972:Glutaminase / Q000737:chemistry; D005973:Glutamine / Q000737:chemistry; D006018:Glycols / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D015233:Models, Statistical; D008969:Molecular Sequence Data; D019884:Nitrogenous Group Transferases / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011732:Pyridoxal Phosphate / Q000737:chemistry*; D012274:Ribulosephosphates / Q000737:chemistry; D013379:Substrate Specificity
chemical_list: D006018:Glycols; D012274:Ribulosephosphates; D005973:Glutamine; C031524:ribulose 5-phosphate; D011732:Pyridoxal Phosphate; D000641:Ammonia; D019884:Nitrogenous Group Transferases; D005972:Glutaminase; C011480:hexylene glycol