Thermodynamic analysis of a molecular chaperone binding to unfolded protein substrates.

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Molecular chaperones are a highly diverse group of proteins that recognize and bind unfolded proteins to facilitate protein folding and prevent nonspecific protein aggregation. The mechanisms by which chaperones bind their protein substrates have been studied for decades. However, there are few reports about the affinity of molecular chaperones for their unfolded protein substrates. Thus, little is known about the relative binding affinities of different chaperones and about the relative binding affinities of chaperones for different unfolded protein substrates. Here we describe the application of SUPREX (stability of unpurified proteins from rates of H-D exchange), an H-D exchange and MALDI-based technique, in studying the binding interaction between the molecular chaperone Hsp33 and four different unfolded protein substrates, including citrate synthase, lactate dehydrogenase, malate dehydrogenase, and aldolase. The results of our studies suggest that the cooperativity of the Hsp33 folding-unfolding reaction increases upon binding with denatured protein substrates. This is consistent with the burial of significant hydrophobic surface area in Hsp33 when it interacts with its substrate proteins. The SUPREX-derived K(d) values for Hsp33 complexes with four different substrates were all found to be within the range of 3-300 nM.





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Xu, Ying, Sebastian Schmitt, Liangjie Tang, Ursula Jakob and Michael C Fitzgerald (2010). Thermodynamic analysis of a molecular chaperone binding to unfolded protein substrates. Biochemistry, 49(6). pp. 1346–1353. 10.1021/bi902010t Retrieved from

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Michael C. Fitzgerald

Professor of Chemistry

Dr. Fitzgerald’s research group is focused on studies of protein folding and function. The group utilizes a combination of covalent labeling strategies (e.g. protein amide H/D exchange and methionine oxidiation) and mass spectrometry techniques to investigate the thermodynamic properties of protein folding and ligand binding reactions. Current research efforts involve: (1) the development new biophysical methods that enable protein folding and stability measurements to be performed on the proteomic scale; and (2) the application of these new methods in the areas of disease detection, diagnosis, and therapy.

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