title: Role of intramolecular disulfides in stability and structure of a noncovalent homodimer.
abstract: The importance of intramolecular disulfides in a noncovalent dimeric protein interleukin-8 (IL-8) has been studied by replacing cysteines in each of the two disulfide pairs with alpha-aminobutyric acid (CH(2)-SH --> CH(2)-CH(3)). Both disulfide mutants are less stable and exist as molten globules in the monomeric state. Interestingly, both mutants dimerize, though with slightly lower affinities compared to the native protein. NMR studies suggest a molten globule-like structure also in the dimeric state. Structures, sequence analysis, and mutagenesis studies have shown that the conserved hydrophobic residues are packed against each other in the protein core and that H bonding and van der Waals interactions stabilize the dimer interface. Deleting either disulfide in IL-8 results in substantial loss in receptor activity, indicating that both disulfides are critical for function in the folded protein. These data together suggest that the packing interactions of the hydrophobic core determine IL-8 monomer fold, that disulfides play only a marginal role in dimer formation, and that the stability imparted by the disulfides is intimately coupled to fold and function.
authors.affiliation: Department of Biochemistry & Molecular Biology, and Sealy Center for Structural Biology & Molecular Biophysics, University of Texas Medical Branch, Galveston, TX 77555, USA.
authors.forename: Lavanya
authors.initials: L
authors.lastname: Rajagopalan
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Chin
authors.forename: Krishna
authors.initials: K
authors.lastname: Rajarathnam
mesh_terms: D019943:Amino Acid Substitution; D000817:Anilino Naphthalenesulfonates; D055592:Biophysical Phenomena; D001703:Biophysics; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D004355:Drug Stability; D005456:Fluorescent Dyes; D016209:Interleukin-8 / Q000737:chemistry / Q000235:genetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D013816:Thermodynamics
chemical_list: D000817:Anilino Naphthalenesulfonates; D004220:Disulfides; D005456:Fluorescent Dyes; D016209:Interleukin-8; D010446:Peptide Fragments; D011506:Proteins; D011994:Recombinant Proteins; C027132:1-anilino-8-naphthalenesulfonate