title: Thermal unfolding of the cytotoxin alpha-sarcin: phospholipid binding induces destabilization of the protein structure.
abstract: The effect of membrane binding on the structure and stability of the cytotoxin alpha-sarcin has been studied by differential scanning calorimetry, Fourier-transform infrared and fluorescence spectroscopic techniques. The thermal unfolding of alpha-sarcin in aqueous solution fits into a two-state transition characterized by a transition temperature (Tm) of 52.6 degrees C and a calorimetric enthalpy (delta Hcal) of 136 kcal/mol. Upon interaction with phosphatidylglycerol vesicles, alpha-sarcin undergoes conformational changes, as deduced from the FTIR and fluorescence emission spectra. These changes result in a decreased Tm and delta Hcal values for the thermal unfolding of phospholipid-bound alpha-sarcin. The lower Tm value for lipid-bound alpha-sarcin is also observed at the level of secondary and tertiary structures, based on analyses of both the amide I' infrared spectrum and the tryptophan emission of the protein as a function of temperature, respectively. The results obtained indicate a protein destabilization promoted by the phospholipid interaction.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense, Madrid, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Gasset
authors.forename: J M
authors.initials: JM
authors.lastname: Mancheño
authors.forename: J
authors.initials: J
authors.lastname: Laynez
authors.forename: J
authors.initials: J
authors.lastname: Lacadena
authors.forename: G
authors.initials: G
authors.lastname: Fernández-Ballester
authors.forename: A
authors.initials: A
authors.lastname: Martinez del Pozo
authors.forename: M
authors.initials: M
authors.lastname: Oñaderra
authors.forename: J G
authors.initials: JG
authors.lastname: Gavilanes
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry*; D001230:Aspergillus; D002152:Calorimetry, Differential Scanning; D004722:Endoribonucleases; D005656:Fungal Proteins / Q000737:chemistry*; D006358:Hot Temperature; D010743:Phospholipids / Q000737:chemistry*; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D011500:Protein Synthesis Inhibitors / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000970:Antineoplastic Agents; D005656:Fungal Proteins; D010743:Phospholipids; D011500:Protein Synthesis Inhibitors; C014801:alpha-sarcin; D004722:Endoribonucleases