title: Removal of the tryptophan 139 side chain in Escherichia coli D-3-phosphoglycerate dehydrogenase produces a dimeric enzyme without cooperative effects.
abstract: Escherichia coli d-3-phosphoglycerate dehydrogenase (PGDH) is a homotetrameric enzyme whose activity is allosterically regulated by l-serine, the end-product of its metabolic pathway. Previous studies have shown that PGDH displays two modes of cooperative interaction. One is between the l-serine binding sites and the other is between the l-serine binding sites and the active sites. Tryptophan 139 participates in an intersubunit contact near the active site catalytic residues. Site-specific mutagenesis of tryptophan 139 to glycine results in the dissociation of the tetramer to a pair of dimers and in the loss of cooperativity in serine binding and between serine binding and inhibition. The results suggest that the magnitude of inhibition of activity at a particular active site is primarily dependent on serine binding to that subunit but that activity can be modulated in a cooperative manner by interaction with adjacent subunits. The disruption of the nucleotide domain interface in PGDH by mutating Trp-139 suggests the potential for a critical role of this interface in the cooperative allosteric processes in the native tetrameric enzyme.
authors.affiliation: Department of Medicine, Washington University School of Medicine, St. Louis, Missouri, 63110, USA. ggrant@molecool.wustl.edu
authors.forename: G A
authors.initials: GA
authors.lastname: Grant
authors.forename: X L
authors.initials: XL
authors.lastname: Xu
authors.forename: Z
authors.initials: Z
authors.lastname: Hu
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects / Q000235:genetics; D001665:Binding Sites; D002237:Carbohydrate Dehydrogenases / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D002850:Chromatography, Gel; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology*; D016297:Mutagenesis, Site-Directed; D050543:Phosphoglycerate Dehydrogenase; D017384:Sequence Deletion / Q000235:genetics; D012694:Serine / Q000378:metabolism / Q000494:pharmacology; D013329:Structure-Activity Relationship; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D012694:Serine; D014364:Tryptophan; D002237:Carbohydrate Dehydrogenases; D050543:Phosphoglycerate Dehydrogenase