Biphasic transition curve on denaturation of chicken cystatin by guanidinium chloride. Evidence for an independently unfolding structural region.
Far-ultraviolet circular dichroism and tryptophan fluorescence measurements showed that the reversible unfolding of the cysteine proteinase inhibitor, chicken cystatin, by guanidinium chloride is a two-step process with transition midpoints at approximately 3.4 and approximately 5.4 M denaturant. The partially unfolded intermediate had both far- and near-ultraviolet circular dichroism and fluorescence emission spectra comparable to those of the native protein. The largely retained tertiary structure suggests that the intermediate represents a species in which a separate region of lower stability has been unfolded, rather than an intermediate of the 'molten globule' type. Such a structurally independent region is apparent in the three-dimensional structure of the inhibitor.
Björk
I
I
Department of Veterinary Medical Chemistry, Swedish University of Agricultural Sciences, Uppsala Biomedical Center, Sweden.
Pol
E
E
D000818:Animals; D002645:Chickens; D002942:Circular Dichroism; D015891:Cystatins / Q000737:chemistry*; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology*; D011487:Protein Conformation; D011489:Protein Denaturation; D013050:Spectrometry, Fluorescence
D015891:Cystatins; D006146:Guanidines; D019791:Guanidine