Guanidine hydrochloride-induced folding of proteins.
Guanidine hydrochloride (Gdn-HCl) is the most commonly used denaturant for proteins. Contrary to expectation, we found that Gdn-HCl at low concentrations refolds acid-unfolded apomyoglobin and cytochrome c, stabilizing the molten globule state, i.e. a compact denatured state with a significant amount of secondary structure, but substantially disordered tertiary structure. A further increase in Gdn-HCl concentration, above 1 M, caused co-operative unfolding of the molten globule state. Similar sequential folding and unfolding transitions were also observed at neutral pH with a synthetic amphiphilic peptide consisting of Lys and Leu residues, indicating the generality of the phenomenon. Although the Gdn-HCl-induced refolding and unfolding transitions were puzzling at first glance, we show that they are readily interpreted in terms of the differential action of Gdn-HCl. We also show that the comparison of the unfolding curves for the molten globule and native states provides a measure of the buried surface area upon formation of the molten globule state.
Department of Biology, Faculty of Science, Osaka University, Japan.
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Hagihara
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Aimoto
A L
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Fink
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Goto
D000595:Amino Acid Sequence; D001059:Apoproteins / Q000737:chemistry* / Q000187:drug effects; D003574:Cytochrome c Group / Q000737:chemistry* / Q000187:drug effects; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009211:Myoglobin / Q000737:chemistry* / Q000187:drug effects; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation / Q000187:drug effects; D011489:Protein Denaturation; D017510:Protein Folding; D013056:Spectrophotometry, Ultraviolet
D001059:Apoproteins; D003574:Cytochrome c Group; D006146:Guanidines; D009211:Myoglobin; D010455:Peptides; C010857:apomyoglobin; D019791:Guanidine