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Thermal unfolding of triosephosphate isomerase from Entamoeba histolytica: dimer dissociation leads to extensive unfolding
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2008 (English)In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 47, no 44, p. 11665-11673Article in journal (Refereed) Published
Abstract [en]

In mesophiles, triosephosphate isomerase (TIM) is an obligated homodimer. We have previously shown that monomeric folding intermediates are common in the chemical unfolding of TIM, where dissociation provides 75% of the overall conformational stability of the dimer. However, analysis of the crystallographic structure shows that, during unfolding, intermonomeric contacts contribute to only 5% of the overall increase in accessible surface area. In this work several methodologies were used to characterize the thermal dissociation and unfolding of the TIM from Entamoeba histolytica (EhTIM) and a monomeric variant obtained by chemical derivatization (mEhTIM). During EhTIM unfolding, sequential transitions corresponding to dimer dissociation into a compact monomeric intermediate followed by unfolding and further aggregation of the intermediate occurred. In the case of mEhTIM, a single transition, analogous to the second transition of EhTIM, was observed. Calorimetric, spectroscopic, hydrodynamic, and functional evidence shows that dimer dissociation is not restricted to localized interface reorganization. Dissociation represents 55% (DeltaH(Diss) = 146.8 kcal mol(-1)) of the total enthalpy change (DeltaH(Tot) = 266 kcal mol(-1)), indicating that this process is linked to substantial unfolding. We propose that, rather than a rigid body process, subunit assembly is best represented by a fly-casting mechanism. In TIM, catalysis is restricted to the dimer; therefore, the interface can be viewed as the final nucleation motif that directs assembly, folding, and function.

Place, publisher, year, edition, pages
2008. Vol. 47, no 44, p. 11665-11673
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Structural Biology
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URN: urn:nbn:se:umu:diva-156773DOI: 10.1021/bi801360kPubMedID: 18837510OAI: oai:DiVA.org:umu-156773DiVA, id: diva2:1291987
Available from: 2019-02-26 Created: 2019-02-26 Last updated: 2019-03-07Bibliographically approved

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Cisneros, David A.

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