Thermal-unfolding Reaction of Triosephosphate Isomerase from Trypanosoma cruzi
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Thermal denaturation of triosephosphate isomerase from Trypanosoma cruzi was studied by circular dicrhoism and fluorescence spectroscopies. The unfolding transition was found to be highly irreversible even at the very early stages of the reaction. Kinetic studies, allowed us to identify consecutive reactions. Firstly, only the tryptophan environment is altered. Next, changes on the secondary structure and hydrophobic surface exposure measured by 1-anilino-8-naphthalenesulfonate (ANS) binding were observed. Further conformational changes imply additional modifications on the secondary and tertiary structures and release of the hydrophobic dye leading to the formation of the unfolded state that is prone to aggregate.
KeywordsTriosephosphate isomerase Thermal unfolding kinetics Molten globule Circular dichroism Irreversibility
Triosephosphate isomerase from Trypanosoma cruzi
Triosephosphate isomerase from Trypanosoma brucei
Yeast triosephosphate isomerase
Spectral centre of mass
We are very grateful to Dr. Armando Gomez Puyou and Beatriz Aguirre for the facilities and help given throughout the purification of TcTIM. EMH received financial support from Instituto Politécnico Nacional and PIFI-IPN (20050356 and 20060916), LMMV thanks economic sustain from CONACyT (175886). This work was supported by grants from TWAS (04–352 RG/BIO/LA), CONACyT (45990 and 46168-M), ECOS m05–501 and SIP-IPN 20070141.
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