To investigate a putatively primordial protein we have simplified the sequence of a 56-residue alpha/beta fold (the immunoglobulin-binding domain of protein G) by replacing it with polyalanine, polythreonine, and diglycine segments at regions of the sequence that in the folded structure are alpha-helical, beta-strand, and turns, respectively. Remarkably, multiple folding and unfolding events ar...

The interaction of 2,2,2-trifluoroethanol (TFE) with concanavalin A has been investigated by using a combination of differential scanning calorimetry, isothermal titration calorimetry (ITC), circular dichroism (CD), and fluorescence spectroscopy at pH 2.5 and 5.2. All of the calorimetric transitions at both the pH values were found to be irreversible. In the presence of 4 mol kg(-1) TFE at pH 2...

Previous CD measurements of changes in the conformation of beta-lactoglobulin at neutral pH as a function of temperature indicated the formation of a molten globule state above approx. 70 degrees C. New CD measurements are reported at temperatures up to 80 degrees C with an instrument on the Daresbury synchrotron radiation source which gives spectra of good signal-to-noise ratio down to 170 nm....

Time-resolved fluorescence experiments were carried out on a variety of apomyoglobins with one or two tryptophan (Trp) residues located at invariant positions 7 and 14 in the primary sequence. In all cases, the Trp fluorescence kinetics were resolved adequately into two discrete lifetime domains, and decay-associated spectra (DAS) were obtained for each decay component. The DAS resolved for unf...

Biological signaling generally involves the activation of a receptor protein by an external stimulus followed by protein-protein interactions between the activated receptor and its downstream signal transducer. The current paradigm for the relay of signals along a signal transduction chain is that it occurs by highly specific interactions between fully folded proteins. However, recent results i...

The folding of globular proteins occurs through intermediate states whose characterisation provides information about the mechanism of folding. A major class of intermediate states is the compact 'molten globule', whose characteristics have been studied intensively in those conditions in which it is stable (at acid pH, high temperatures and intermediate concentrations of strong denaturants). In...

The calcium binding protein alpha-lactalbumin folds via a molten globule intermediate. Calcium does not bind strongly to the unfolded protein or the molten globule, but does bind to the transition state between the molten globule and the native protein. Of interest are the structures formed in the transition state that promote calcium binding. To study the importance of local secondary structur...

Alphab-crystallin, a small heat-shock protein has been shown to prevent the aggregation of other proteins under various stress conditions. We have investigated the role of alphaB-crystallin in the reactivation of denaturant [GdmCl (guanidinium chloride)]-inactivated G6PD (glucose-6-phosphate dehydrogenase). Studies indicate that unfolding and inactivation of G6PD by GdmCl proceeds via formation...

Recent reports give strong support to the idea that amyloid fibril formation and the subsequent development of protein deposition diseases originate from conformational changes in corresponding amyloidogenic proteins. In this review, recent findings are surveyed to illustrate that protein fibrillogenesis requires a partially folded conformation. This amyloidogenic conformation is relatively unf...

Recent advances in the field of protein chemistry have significantly enhanced our understanding of the possible intermediates that may occur during protein folding and unfolding. In particular, studies on alpha-lactalbumin have led to the theory that the molten globule state may be a possible intermediate in the folding of many proteins. The molten globule state is characterized by a somewhat c...