title: Long-range cooperative binding effects in a T cell receptor variable domain.
abstract: Although cellular processes depend on protein-protein interactions, our understanding of molecular recognition between proteins remains far from comprehensive. Protein-protein interfaces are structural and energetic mosaics in which a subset of interfacial residues, called hot spots, contributes disproportionately to the affinity of the complex. These hot-spot residues can be further clustered into hot regions. It has been proposed that binding energetics between residues within a hot region are cooperative, whereas those between hot regions are strictly additive. If this idea held true for all protein-protein interactions, then energetically significant long-range conformational effects would be unlikely to occur. In the present study, we show cooperative binding energetics between distinct hot regions that are separated by >20 A. Using combinatorial mutagenesis and surface plasmon resonance binding analysis to dissect additivity and cooperativity in a complex formed between a variable domain of a T cell receptor and a bacterial superantigen, we find that combinations of mutations from each of two hot regions exhibited significant cooperative energetics. Their connecting sequence is composed primarily of a single beta-strand of the T cell receptor variable Ig domain, which has been observed to undergo a strand-switching event and does not form an integral part of the stabilizing core of this Ig domain. We propose that these cooperative effects are propagated through a dynamic structural network. Cooperativity between hot regions has significant implications for the prediction and inhibition of protein-protein interactions.
authors.affiliation: Boston Biomedical Research Institute, Watertown, MA 02472, USA.
authors.forename: Beenu
authors.initials: B
authors.lastname: Moza
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Buonpane
authors.forename: Penny
authors.initials: P
authors.lastname: Zhu
authors.forename: Christine A
authors.initials: CA
authors.lastname: Herfst
authors.forename: A K M Nur-ur
authors.initials: AK
authors.lastname: Rahman
authors.forename: John K
authors.initials: JK
authors.lastname: McCormick
authors.forename: David M
authors.initials: DM
authors.lastname: Kranz
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Sundberg
mesh_terms: D001427:Bacterial Toxins / Q000737:chemistry*; D004768:Enterotoxins / Q000737:chemistry*; D006801:Humans; D016296:Mutagenesis; D009154:Mutation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000737:chemistry* / Q000235:genetics; D018089:Superantigens / Q000737:chemistry*; D020349:Surface Plasmon Resonance
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D016693:Receptors, Antigen, T-Cell, alpha-beta; D018089:Superantigens; C030107:enterotoxin F, Staphylococcal