title: Formation of an alpha-helix in human tumor necrosis factor-alpha by guanidine hydrochloride-induced unfolding.
abstract: Human tumor necrosis factor-alpha (TNF-alpha) is a trimeric protein consisting primarily of beta-sheet. GdnHCl-induced unfolding of TNF-alpha was investigated at room temperature by circular dichroism (CD) and size exclusion chromatography. The secondary and tertiary structure of TNF-alpha persisted up to 0.9N GdnHCl regardless of incubation time, but, in the range of 1.2 N to 2.1 N GdnHCl, there was loss of tertiary structure accompanied by the formation of an alpha-helix, as revealed by far- and near-UV CD spectra. The structural changes occurred gradually in 1.2 and 2.1 N GdnHCl, but were rapid in 1.5 and 1.8 N GdnHCl. The GdnHCl-induced state of TNF-alpha is an unfolded, alpha-helical aggregate of about 130 monomers, as shown by size exclusion chromatography. We suggest the most likely pathway for the transition from beta-sheet to alpha-helix.
authors.affiliation: Department of Bioinformatics and Life Science, and Computer-Aided Molecular Design Research Center, Soongsil University, Seoul 156-743, Korea.
authors.forename: Woojin
authors.initials: W
authors.lastname: Jeong
authors.forename: Hang-Cheol
authors.initials: HC
authors.lastname: Shin
mesh_terms: D002845:Chromatography; D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D019791:Guanidine / Q000737:chemistry*; D006801:Humans; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D013696:Temperature; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D019791:Guanidine