title: Structural basis of affinity maturation and intramolecular cooperativity in a protein-protein interaction.
abstract: Although protein-protein interactions are involved in nearly all cellular processes, general rules for describing affinity and selectivity in protein-protein complexes are lacking, primarily because correlations between changes in protein structure and binding energetics have not been well determined. Here, we establish the structural basis of affinity maturation for a protein-protein interaction system that we had previously characterized energetically. This model system exhibits a 1500-fold affinity increase. Also, its affinity maturation is restricted by negative intramolecular cooperativity. With three complex and six unliganded variant X-ray crystal structures, we provide molecular snapshots of protein interface remodeling events that span the breadth of the affinity maturation process and present a comprehensive structural view of affinity maturation. Correlating crystallographically observed structural changes with measured energetic changes reveals molecular bases for affinity maturation, intramolecular cooperativity, and context-dependent binding.
authors.affiliation: Center for Advanced Research in Biotechnology, W.M. Keck Laboratory for Structural Biology, University of Maryland Biotechnology Institute, Rockville, Maryland 20850, USA.
authors.forename: Sangwoo
authors.initials: S
authors.lastname: Cho
authors.forename: Chittoor P
authors.initials: CP
authors.lastname: Swaminathan
authors.forename: Jianying
authors.initials: J
authors.lastname: Yang
authors.forename: Melissa C
authors.initials: MC
authors.lastname: Kerzic
authors.forename: Rongjin
authors.initials: R
authors.lastname: Guan
authors.forename: Michele C
authors.initials: MC
authors.lastname: Kieke
authors.forename: David M
authors.initials: DM
authors.lastname: Kranz
authors.forename: Roy A
authors.initials: RA
authors.lastname: Mariuzza
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Sundberg
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D018360:Crystallography, X-Ray; D004768:Enterotoxins / Q000737:chemistry* / Q000235:genetics; D051379:Mice; D008958:Models, Molecular; D009154:Mutation; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000737:chemistry* / Q000235:genetics; D014867:Water / Q000737:chemistry
chemical_list: D004768:Enterotoxins; D010446:Peptide Fragments; D016693:Receptors, Antigen, T-Cell, alpha-beta; C109168:T-cell receptor Vbeta 8.2; D014867:Water; C034959:enterotoxin C, staphylococcal