Thermodynamic stability of the molten globule states of apomyoglobin.


Whereas horse apomyoglobin is fully unfolded at pH 2 in the absence of salt, addition of a salt such as sodium chloride or sodium trichloroacetate stabilizes the molten globule state. Thermal unfolding of the salt-stabilized molten globule states of horse apomyoglobin at pH 2 measured by far-UV circular dichroism occurs not only on heating (i.e. heat-denaturation) but also on cooling (i.e. cold-denaturation). This demonstrates that a hydrophobic interaction contributes to the stability of the molten globule state and suggests that the unfolding transition can be represented by a cooperative two-state mechanism. To clarify the mechanism of conformational transition, we investigated the thermal unfolding of the chloride-stabilized molten globule state by differential scanning calorimetry. We observed a broad but distinct excess heat capacity peak, which is consistent with the unfolding transition measured by circular dichroism. To further characterize the molten globule states, we examined by far-UV circular dichroism the denaturant-induced unfolding transitions of the molten globule states stabilized by sodium chloride or sodium trichloroacetate. The urea-induced unfolding transitions of the molten globule states were explained by the two-state mechanism. The guanidine-hydrochloride-induced unfolding experiments clarified that the trichloroacetate-stabilized molten globule state is distinct from the chloride-stabilized one and that the former involves additional helical segment(s). These results support a view that the thermal unfolding of the molten globule states at pH 2 can be approximated by a two-state transition. However, several results suggested that a combined mechanism incorporating the two-state transition and a gradual structural change would be more general in describing the conformational transition of the molten globule states. Study holds ProTherm entries: 7479, 7480, 7481, 7482, 7483, 7484 Extra Details: apomyoglobin; differential scanning calorimetry;,hydrophobic interactions; molten globule; protein folding

Submission Details

ID: chSb8C2n

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:34 p.m.

Version: 1

Publication Details
Nishii I;Kataoka M;Goto Y,J. Mol. Biol. (1995) Thermodynamic stability of the molten globule states of apomyoglobin. PMID:7608972
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Myoglobin P68083 MYG_EQUBU
100.0 Myoglobin P68082 MYG_HORSE
91.6 Myoglobin P02181 MYG_INIGE
92.2 Myoglobin P02169 MYG_LEPMU
90.9 Myoglobin P02166 MYG_PERPO
90.9 Myoglobin P02189 MYG_PIG
90.8 Myoglobin Q0KIY1 MYG_BALBO
90.8 Myoglobin Q0KIY2 MYG_BALED
90.8 Myoglobin P02177 MYG_ESCRO
90.3 Myoglobin P02183 MYG_MESCA
90.3 Myoglobin Q0KIY0 MYG_MESST
90.3 Myoglobin P02167 MYG_NYCCO
90.3 Myoglobin P02165 MYG_TUPGL
90.9 Myoglobin P11343 MYG_LUTLU
90.3 Myoglobin P02163 MYG_ROUAE
90.1 Myoglobin P02178 MYG_MEGNO