title: A conserved hydrogen-bond network stabilizes the structure of Beta class glutathione S-transferases.
abstract: We identified a network of hydrogen bonds that is conserved in the structures of bacterial Beta class glutathione S-transferases (GSTs). It is formed by three residues: a serine, a histidine and a glutamate, together with a water molecule that links the serine with the histidine. This network connects the first helix of the N-terminal glutaredoxin-like domain with the last helix of the C-terminal GST-specific all helical domain. Here we show that substitution of Ochrobactrum anthropi GST His15 and Glu198 with alanine greatly compromises the catalytic efficiency of the enzyme, even though none of these residues takes part to the enzyme active site. Thermal and chemical denaturation experiments point to a role for this network in global structure stabilization. Furthermore, we show that OaGST structure looses compactness at alkanine pHs and that this behavior may be ascribed to partial disruption of the H-bond network, pointing to an important role in zippering the N-terminal and C-terminal domains of the protein.
authors.affiliation: Ce.S.I. Center for Studies on Aging, University of Chieti G. D'Annunzio, Via dei Vestini 31, 66013 Chieti, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Federici
authors.forename: Michele
authors.initials: M
authors.lastname: Masulli
authors.forename: Stefano
authors.initials: S
authors.lastname: Gianni
authors.forename: Carmine
authors.initials: C
authors.lastname: Di Ilio
authors.forename: Nerino
authors.initials: N
authors.lastname: Allocati
mesh_terms: D000409:Alanine / Q000737:chemistry / Q000235:genetics; D019943:Amino Acid Substitution; D002384:Catalysis; D020134:Catalytic Domain / Q000235:genetics; D018360:Crystallography, X-Ray; D004795:Enzyme Stability; D018698:Glutamic Acid / Q000737:chemistry* / Q000235:genetics; D005982:Glutathione Transferase / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry* / Q000235:genetics; D006860:Hydrogen Bonding; D020621:Ochrobactrum anthropi / Q000201:enzymology*
chemical_list: D018698:Glutamic Acid; D006639:Histidine; D005982:Glutathione Transferase; D000409:Alanine