title: Engineering of betabellin 14D: disulfide-induced folding of a beta-sheet protein.
abstract: The betabellin target structure consists of 2 32-residue beta sheets packed against each other by hydrophobic interactions. We have designed, chemically synthesized, and biophysically characterized betabellin 14S, a single chain, and betabellin 14D, the disulfide-bridged double chain. The 32-residue nongenetic betabellin-14 chain (HSLTASIkaLTIHVQakTATCQVkaYTVHISE, a = D-Ala, k = D-Lys) has a palindromic pattern of polar (p), nonpolar (n), end (e), and beta-turn (t,r) residues (epnpnpnttnpnpnprrpnpnpnttnpnpnpe). Each half contains the same 14-residue palindromic pattern (underlined). Pairs of D-amino acid residues are used to favor formation of inverse-common (type-I') beta turns. In water at pH 6.5, the single chain of betabellin 14S is not folded, but the disulfide-linked betabellin 14D is folded into a stable beta-sheet structure. Thus, folding of the covalent dimer beta-bellin 14D is induced by formation of the single interchain disulfide bond. The binary pattern of alternating polar and nonpolar residues of its beta-sheets is not sufficient to induce folding. Betabellin 14D is a very water-soluble (10 mg/mL), small (64 residues), nongenetic (12 D residues) beta-sheet protein with properties (well-dispersed proton NMR resonances; Tm = 58 degrees C and delta Hm = 106 kcal/mol at pH 5.5) like those of a native protein structure.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, 27599.
authors.forename: Y
authors.initials: Y
authors.lastname: Yan
authors.forename: B W
authors.initials: BW
authors.lastname: Erickson
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D004220:Disulfides / Q000494:pharmacology*; D015195:Drug Design; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011489:Protein Denaturation; D015202:Protein Engineering; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000138:chemical synthesis*; D012091:Repetitive Sequences, Nucleic Acid; D013816:Thermodynamics
chemical_list: D004220:Disulfides; D046911:Macromolecular Substances; D011506:Proteins; C089955:betabellin 14