Total proteins and 11S protein fraction (Helianthinin) of sunflower seed (Helianthus annuus L.) — Effect of acetylation and succinylation

Abstract

SummaryThe total proteins and helianthinin (11s) from sunflower seeds were chemically modified by acetylation and succinylation. The extent of acetylation of the total proteins and helianthinin were 12%, 51%, 52%, 56% and 12%, 36%, 69%, 71%, respectively, while the extent of succinylation were 8%, 21%, 33%, 49% and lo%, 30%, 44%. 61%. respectively. The extent of modification was monitored by the availability of free lysyl residues in the proteins. The ultraviolet absorption maximum shiftcd to higher wavelengths in total proteins and in helianthinin; there was also an increase in absorbance in the 260 nm wavelength, as a function of increased chemical modification. The sedimentation velocity profile indicated the dissociation of the proteins to low molecular weight fraction (2s) through a 7s component. The dissociation occurred at low modification levels in both total proteins and in helianthinin. There was a gradual red shift and quenching in the fluorescence emission maximum at higher modification levels indicating the denaturation of the proteins as a result of this chemical modification. The change in absorbance as a function of temperature indicates minor changes suggesting that the conformation of the proteins is already altered to significant extents due to the chemical modification. Zusammenfassung

Grafting of Aliphatic and Aromatic Probes on Rapeseed 2S and 12S Proteins: Influence on Their Structural and Physicochemical Properties

“…This was probably the result of an expansion of the protein (Kronman and Holmes, 1969;Chen et al, 1969), a conclusion in accordance with the greater random coil structure of modified 12S as suggested by far-UV CD spectra (Table 3). Venktesh and Prakash (1994) also observed a quenching and a red shift of the fluorescence emission as a result of increasing degrees of acetylation or succinylation of 11S proteins from sunflower seed. They interpreted these results as a progressive dissociation at lower modification levels and denaturation of the 11S at higher modification levels, resulting in exposure of the tryptophanyl groups from the interior of the protein to the aqueous solvent.…”

The relationships between physicochemical properties and conformational features of succinylated and acetylated kidney bean (Phaseolus vulgaris L.) protein isolates

“…Similar phenomena of 'critical degree of modification' have been observed for acetylated and/or succinylated sunflower 11S globulins (Venktesh & Prakash, 1994) and a-globulin from Sesamum indicum (Zaghloul & Prakash, 2002), though in these cases, the change in tertiary conformation was evaluated using intrinsic fluorescence spectroscopic technique.…”