A specific three dimensional (3D) structure of a protein critically defines its conformational stability providing definite function to that protein. Interplay of physiochemical forces like hydrophobic interactions, ionic interactions, disulphide bonds and van der Waals forces impart precise 3D structure to a protein as they are involved at various stages of its folding-unfolding. So a profound comprehension of these physicochemical interactions involved would directly affect the approach to elucidate the transition stages during folding-unfolding of a protein. (doi: 10.1016/j.ijbiomac.2017.07.172)

Phytocystatin, a sub family of cys-tatin are involved in regulating various physiological activities of plants as well as in endogenous cysteine protease activity during seed maturation and germination. And Garlic is a medicinal plant and exhibits immense therapeutic potential in pharmaceutical industry. Beno et al (doi: 10.1016/j.ijbiomac.2017.07.172) have isolated garlic phytocystatin (GPC) and investigated it under denaturing conditions of urea and guanidine hydrochloride. Various biophysical parameters were checked during the unfolding of GPC which describes structure–function relationships on the basis of conformational changes caused by denaturants.

Intrinsic fluorescence, circular dichroism and FTIR were used to investigate an altered structure of garlic phytocystatin with increasing concentration of denaturant. The inhibitory activity of GPC decreases with increasing concentration of denaturant. Guanidine hydrochloride induced unfolding showed presence of indiscernible intermediate as by 8-Anilino-1-Naphthalene-Sulphonic acid binding studies. This is not the case in the course of denaturation by urea. Mid-point transition was observed at 4.7 ± 0.1 M urea and 2.32 ± 0.1 M Guanidine hydrochloride. Circular dichroism and FTIR results indicate the 50% loss of secondary structure at 5 M urea and 2.5 M guanidine hydrochloride.

In a word, the chemical denaturation of phytocystatin was done with the aid of urea and guanidine hydrochloride. Normal functioning of phytocystatin is required to maintain the physiological balance and development of plants. The unfolding pattern of phytocystatin was monitored by intrinsic fluorescence, circular dichroism and FTIR spectroscopy which suggest the complete unfolding at 8 M urea and 4 M guanidine hydrochloride.

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