title: Partially folded states of the cytolytic protein sticholysin II.
abstract: Sticholysin II (Stn II) is a cytolytic protein produced by the sea anemone Stichodactyla helianthus, its effect being related to pore formation. The conformation of the protein and its temperature-induced transitions, in the 1.5-12.0 pH range and in the 0-0.5 M NaCl concentration interval, have been studied by circular dichroism and fluorescence spectroscopy. At temperature < 35 degrees C, the protein maintains the same, high beta-structure content, folded conformation in the 1.5-11.0 pH range and ionic strength up to 0.5 M. In the 1.5-3.5 pH range and ionic strength > or = 0.1 M, Stn II shows a thermal transition, resulting in a partially folded state characterized by: (i) a native-like content of regular secondary structure, as detected by far-UV CD; (ii) a largely disordered tertiary structure, as detected by near-UV CD, with partially exposed tryptophan residues according to their fluorescence emission; and (iii) ability to bind the hydrophobic probe 2-anilinonaphthalene-6-sulfonic acid. In the pH range 4.0-10.5, thermally-induced protein aggregation occurs. The obtained results demonstrate the existence of partially folded state of Stn II, which may contribute to the pore formation ability of this cytolysin.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense, Madrid, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Mancheño
authors.forename: V
authors.initials: V
authors.lastname: De Los Ríos
authors.forename: A
authors.initials: A
authors.lastname: Martínez Del Pozo
authors.forename: M E
authors.initials: ME
authors.lastname: Lanio
authors.forename: M
authors.initials: M
authors.lastname: Oñaderra
authors.forename: J G
authors.initials: JG
authors.lastname: Gavilanes
mesh_terms: D000817:Anilino Naphthalenesulfonates / Q000378:metabolism; D002942:Circular Dichroism; D003064:Cnidarian Venoms / Q000737:chemistry*; D006460:Hemolysin Proteins / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009994:Osmolar Concentration; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012965:Sodium Chloride / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D013696:Temperature
chemical_list: D000817:Anilino Naphthalenesulfonates; D003064:Cnidarian Venoms; D006460:Hemolysin Proteins; C404794:sticholysin II; C047136:2-anilinonaphthalene-6-sulfonic acid; D012965:Sodium Chloride