title: A conserved interdomain interaction is a determinant of folding cooperativity in the GST fold.
abstract: The canonical glutathione transferase (GST) fold found in many monomeric and dimeric proteins consists of two domains that differ in structure and conformational dynamics. However, no evidence exists that the two domains unfold/fold independently at equilibrium, indicating the significance of interdomain interactions in governing cooperativity between domains. Bioinformatics analyses indicate the interdomain interface of the GST fold is large, predominantly hydrophobic with a high packing density explaining cooperative interdomain behavior. Structural alignments reveal a topologically conserved lock-and-key interaction across the domain interface in which a bulky hydrophobic residue ("key") protrudes from the surface of the N-domain and inserts into a pocket ("lock") in the C-domain. To better understand the molecular basis for the contribution of interdomain interactions toward cooperativity within the GST fold in the absence of any influence from quaternary interactions, studies were done with two monomeric GST proteins: Escherichia coli Grx2 (EcGrx2) and human CLIC1 (hCLIC1). Replacing the methionine "key" residue with alanine is structurally nondisruptive, whereas it significantly diminishes the folding cooperativity of both proteins. The loss in cooperativity between domains in the mutants is reflected by a change in the equilibrium folding mechanism from a wild-type two-state process to a three-state process, populating a stable folding intermediate.
authors: Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa.
authors: Nishal
authors: N
authors: Parbhoo
authors: Stoyan H
authors: SH
authors: Stoychev
authors: Sylvia
authors: S
authors: Fanucchi
authors: Ikechukwu
authors: I
authors: Achilonu
authors: Roslin J
authors: RJ
authors: Adamson
authors: Manuel
authors: M
authors: Fernandes
authors: Samantha
authors: S
authors: Gildenhuys
authors: Heini W
authors: HW
authors: Dirr
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D017931:DNA Primers; D005982:Glutathione Transferase / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D016297:Mutagenesis, Site-Directed; D011487:Protein Conformation; D017510:Protein Folding; D013056:Spectrophotometry, Ultraviolet
chemical_list: D017931:DNA Primers; D005982:Glutathione Transferase