Design of single-layer β-sheets without a hydrophobic core

• Published in: Nature (London) 2000-01, Vol.403 (6768), p.456-460
• Main Authors: Koide, Shohei, Huang, Xiaolin, Link, Karl, Koide, Akiko, Bu, Zimei, Engelman, Donald M
• Format: Article
• Language: English
• Subjects: Antigens, Surface - chemistry; Antigens, Surface - genetics; Bacterial Outer Membrane Proteins - chemistry; Bacterial Outer Membrane Proteins - genetics; Bacterial Vaccines; Bacteriology; Biochemistry; Biogenesis of cell structures, supramolecular organization; Biological and medical sciences; Borrelia burgdorferi; Borrelia burgdorferi Group; Deuterium; Fundamental and applied biological sciences. Psychology; Humanities and Social Sciences; letter; Lipoproteins; Magnetic Resonance Spectroscopy; Microbiology; multidisciplinary; NMR; Nuclear magnetic resonance; OspA protein; Protein Denaturation; Protein Folding; Protein Structure, Secondary; Proteins; Scattering, Radiation; Science; Science (multidisciplinary); Solvents; Thermodynamics; Water
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/35000255

The hydrophobic effect is the main thermodynamic driving force in the folding of water-soluble proteins. Exclusion of nonpolar moieties from aqueous solvent results in the formation of a hydrophobic core in a protein, which has been generally considered essential for specifying and stabilizing the folded structures of proteins. Outer surface protein A (OspA) from Borrelia burgdorferi contains a three-stranded β-sheet segment which connects two globular domains. Although this single-layer β-sheet segment is exposed to solvent on both faces and thus does not contain a hydrophobic core, the segment has a high conformational stability. Here we report the engineering of OspA variants that contain larger single-layer β-sheets (comprising five and seven β-strands) by duplicating a β-hairpin unit within the β-sheet. Nuclear magnetic resonance and small-angle X-ray scattering analyses reveal that these extended single-layer β-sheets are formed as designed, and amide hydrogen-deuterium exchange and chemical denaturation show that they are stable. Thus, interactions within the β-hairpin unit and those between adjacent units, which do not involve the formation of a hydrophobic core, are sufficient to specify and stabilize the single-layer β-sheet structure. Our results provide an expanded view of protein folding, misfolding and design.