SPECTROSCOPIC STUDIES ON THE CONFORMATION OF NATIVE and DENATURED GLYCININ

Abstract

Optical rotatory dispersion (ORD) studies and infrared spectra in deuterium oxide indicate that native glycinin exhibits mainly a β‐conformation structure. Ultraviolet difference spectra showed that urea ami guanidine hydrochloride at increasing concentrations cause progressive exposure of tyrosine and tryptophan residues. Ultraviolet difference spectroscopy was also used in following the course of acid‐induced denaturation of glycinin. It was observed that acid denaturation starts approximately at pH 3.50 reaching a maximum at pH 2.0. Data obtained by solvent perturbation of native glycinin using perturbants exhibiting mean diameters of 2.0, 4.4, and 7.2 A indicate that approximately 34 to 37 residues (45%of the total) are accessible to these perturbants whereas the accessibility of tryptophan residues is decreased with increasing mean diameters of the perturbant.

A Circular Dichroism and Fluorescence Spectrometric Assessment of Effects of Selected Chemical Denaturants on Soybean (Glycine max L.) Storage Proteins Glycinin (11S) and β-Conglycinin (7S)

“…Estimation of secondary structure from the recorded CD spectra indicated predominance of β-strands (38.6% in 11S and 36.6% in 7S), with ∼10% α-helices. In general, our findings are in agreement with the literature – . From the CD spectra, we conclude that native soybean proteins belong to the β-I class of proteins; i.e., the β-sheet content of soybean proteins is significantly higher than random secondary structure content .…”

Acid denaturation of mustard 12S protein

“…The decrease in blue shift observed below pH 2.5 could also be due t o either refolding of the denatured protein or reaggregation of the dissociated subunits or both. Similar observations of initial increase in blue shift (up to pH 2.5-3.0) in the difference spectrum followed by a decrease in the blue shift at lower pH values have been reported in the case of a number of proteins, both single chain (human carbonic anhydrase B, (24)) and oligomeric (glycinin, (25,26), sesame a-globulin (8), and arachin (27)).…”