Tags

Type your tag names separated by a space and hit enter

Thermodynamic stability of the molten globule states of apomyoglobin.
J Mol Biol. 1995 Jul 07; 250(2):223-38.JM

Abstract

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.

Links

Publisher Full Text

Authors+Show Affiliations

Nishii I
Department of Biology, Faculty of Science Osaka University, Toyonaka, Japan.
Kataoka M
No affiliation info available
Goto Y
No affiliation info available

MeSH

AnimalsApoproteinsCalorimetry, Differential ScanningCircular DichroismGuanidineGuanidinesHorsesMyoglobinProtein DenaturationProtein FoldingThermodynamicsUrea

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

7608972

Citation

Nishii, I, et al. "Thermodynamic Stability of the Molten Globule States of Apomyoglobin." Journal of Molecular Biology, vol. 250, no. 2, 1995, pp. 223-38.
Nishii I, Kataoka M, Goto Y. Thermodynamic stability of the molten globule states of apomyoglobin. J Mol Biol. 1995;250(2):223-38.
Nishii, I., Kataoka, M., & Goto, Y. (1995). Thermodynamic stability of the molten globule states of apomyoglobin. Journal of Molecular Biology, 250(2), 223-38.
Nishii I, Kataoka M, Goto Y. Thermodynamic Stability of the Molten Globule States of Apomyoglobin. J Mol Biol. 1995 Jul 7;250(2):223-38. PubMed PMID: 7608972.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Thermodynamic stability of the molten globule states of apomyoglobin. AU - Nishii,I, AU - Kataoka,M, AU - Goto,Y, PY - 1995/7/7/pubmed PY - 1995/7/7/medline PY - 1995/7/7/entrez SP - 223 EP - 38 JF - Journal of molecular biology JO - J Mol Biol VL - 250 IS - 2 N2 - 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. SN - 0022-2836 UR - https://www.unboundmedicine.com/medline/citation/7608972/Thermodynamic_stability_of_the_molten_globule_states_of_apomyoglobin_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0022-2836(85)70373-7 DB - PRIME DP - Unbound Medicine ER -