Comparative fourier transform infrared and circular dichroism spectroscopic analysis of alpha1-proteinase inhibitor and ovalbumin in aqueous solution.
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.
Dong
A
A
Department of Chemistry and Biochemistry, University of Northern Colorado, Greeley 80639, USA. adong@unco.edu
Meyer
J D
JD
Brown
J L
JL
Manning
M C
MC
Carpenter
J F
JF
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*
D011994:Recombinant Proteins; D000515:alpha 1-Antitrypsin; D010047:Ovalbumin