Multistate unfolding of α-mannosidase from Canavalia ensiformis (Jack Bean): Evidence for the thermostable molten globule

The Molten Globule State of a Globular Protein in a Cell Is More or Less Frequent Case Rather than an Exception

Quite a long time ago, Oleg B. Ptitsyn put forward a hypothesis about the possible functional significance of the molten globule (MG) state for the functioning of proteins. MG is an intermediate between the unfolded and the native state of a protein. Its experimental detection and investigation in a cell are extremely difficult. In the last decades, intensive studies have demonstrated that the MG-like state of some globular proteins arises from either their modifications or interactions with protein partners or other cell components. This review summarizes such reports. In many cases, MG was evidenced to be functionally important. Thus, the MG state is quite common for functional cellular proteins. This supports Ptitsyn’s hypothesis that some globular proteins may switch between two active states, rigid (N) and soft (MG), to work in solution or interact with partners.

Effect of polyethylene glycols on the alkaline-induced molten globule intermediate of bovine serum albumin

In the present study, the formation of one molten globule-like unfolding intermediate of bovine serum albumin (BSA) at pH 11.2 has been established with the help of circular dichroism (CD) spectra, fluorescence spectroscopy and 'phase diagram' approach. Additionally, we have shown the conformational changes occurring in the pH 11.2 intermediate of BSA when it was exposed to different molecular weight polyethylene glycols (PEGs) at varying concentrations. When the pH 11.2 intermediate of BSA was treated by PEG 400 there was induction of secondary and non-native tertiary contacts. In case of PEG 8000 and PEG 20,000, the loss in secondary as well as tertiary structure was observed. PEG 8000 and 20,000 altered the conformation of the pH 11.2 intermediate and resulted in its transition to another intermediate state in which the hydrophobic patches were inaccessible.