title: The hydrophobic lock-and-key intersubunit motif of glutathione transferase A1-1: implications for catalysis, ligandin function and stability.
abstract: A hydrophobic lock-and-key intersubunit motif involving a phenylalanine is a major structural feature conserved at the dimer interface of classes alpha, mu and pi glutathione transferases. In order to determine the contribution of this subunit interaction towards the function and stability of human class alpha GSTA1-1, the interaction was truncated by replacing the phenylalanine 'key' Phe-51 with serine. The F51S mutant protein is dimeric with a native-like core structure indicating that Phe-51 is not essential for dimerization. The mutation impacts on catalytic and ligandin function suggesting that tertiary structural changes have occurred at/near the active and non-substrate ligand-binding sites. The active site appears to be disrupted mainly at the glutathione-binding region that is adjacent to the lock-and-key intersubunit motif. The F51S mutant displays enhanced exposure of hydrophobic surface and ligandin function. The lock-and-key motif stabilizes the quaternary structure of hGSTA1-1 at the dimer interface and the protein concentration dependence of stability indicates that the dissociation and unfolding processes of the mutant protein remain closely coupled.
authors.affiliation: Protein Structure-Function Research Programme, Department of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: Y
authors.initials: Y
authors.lastname: Sayed
authors.forename: L A
authors.initials: LA
authors.lastname: Wallace
authors.forename: H W
authors.initials: HW
authors.lastname: Dirr
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001483:Base Sequence; D002384:Catalysis; D017931:DNA Primers; D004795:Enzyme Stability; D005982:Glutathione Transferase / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D007527:Isoenzymes; D005982:Glutathione Transferase; C119995:glutathione S-transferase alpha