A gradual disruption of tight side-chain packing: 2D 1H-NMR characterization of acid-induced unfolding of CHABII.
Little is known about the mechanism of the transition between native proteins and partially folded intermediates. Complete assignments of 2D 1H-NOESY spectra of CHABII at 5 degrees C, pH 6.3, 5.5, 4.6 and 4.0, reveal that lowering of pH results in an extensive but gradual disappearance of NOEs, implying a gradual disruption of tight side-chain packing. Moreover, a tertiary packing core is identified at 5 degrees C and pH 4.0, characterized by persistent long-range NOEs. Thus, we suggest that severe disruption of tight side-chain packing of CHABII can occur at a stage where its secondary structure and tertiary topology remain highly native-like.
Département d'Ingénierie et d'Etudes des Protéines, CEA, Saclay, Gif-sur-Yvette, France. jsong@bri.nrc.ca
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Song
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Jamin
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Gilquin
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D000143:Acids / Q000737:chemistry; D000595:Amino Acid Sequence; D018999:Charybdotoxin / Q000031:analogs & derivatives; D003080:Cold Temperature; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*
D000143:Acids; C117322:CHABII protein; D011506:Proteins; D018999:Charybdotoxin