title: Comparative fourier transform infrared and circular dichroism spectroscopic analysis of alpha1-proteinase inhibitor and ovalbumin in aqueous solution.
abstract: Alpha1-proteinase inhibitor (alpha1Pi) and ovalbumin are both members of the serpin superfamily. They share about a 30% sequence identity and exhibit great similarity in their three-dimensional structures. However, no apparent functional relationship has been found between the two proteins. Unlike alpha1Pi, ovalbumin shows no inhibitory effect to serine proteases. To see whether or not a conformational factor(s) may contribute to the functional difference, we carried out comparative analysis of the two proteins' secondary structure, thermal stability, and H-D exchange using FT-IR and CD spectroscopy. FT-IR analysis reveals significant differences in the amide I spectral patterns of the two proteins. Upon thermal denaturation, both proteins exhibit a strong low-wavenumber beta-sheet band at 1624 cm(-1) and a weak high-wavenumber beta-sheet band at 1694 cm(-1), indicative of intermolecular aggregate formation. However, the midpoint of the thermal-induced transition of alpha1Pi (approximately 55 degrees C) is 18 degrees C lower than that of ovalbumin (approximately 73 degrees C). The thermal stability analysis provides new insight into the structural changes associated with denaturation. The result of H-D exchange explains some puzzling spectral differences between the two proteins in D2O reported previously.
authors.affiliation: Department of Chemistry and Biochemistry, University of Northern Colorado, Greeley 80639, USA. adong@unco.edu
authors.forename: A
authors.initials: A
authors.lastname: Dong
authors.forename: J D
authors.initials: JD
authors.lastname: Meyer
authors.forename: J L
authors.initials: JL
authors.lastname: Brown
authors.forename: M C
authors.initials: MC
authors.lastname: Manning
authors.forename: J F
authors.initials: JF
authors.lastname: Carpenter
mesh_terms: D002942:Circular Dichroism; D006801:Humans; D010047:Ovalbumin / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D000515:alpha 1-Antitrypsin / Q000737:chemistry*
chemical_list: D011994:Recombinant Proteins; D000515:alpha 1-Antitrypsin; D010047:Ovalbumin