1ytc
From Proteopedia
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THERMODYNAMIC CYCLES AS PROBES OF STRUCTURE-FUNCTION RELATIONSHIPS IN UNFOLDED PROTEINS
Overview
The relationship between structure and stability has been investigated for, the folded forms and the unfolded forms of iso-2 cytochrome c and a, variant protein with a stability-enhancing mutation, N52I iso-2., Differential scanning calorimetry has been used to measure the reversible, unfolding transitions for the proteins in both heme oxidation states., Reduction potentials have been measured as a function of temperature for, the folded forms of the proteins. The combination of measurements of, thermal stability and reduction potential gives three sides of a, thermodynamic cycle and allows prediction of the reduction potential of, the thermally unfolded state. The free energies of electron binding for, the thermally unfolded proteins differ from those expected for a fully, unfolded protein, suggesting that residual structure modulates the, reduction potential. At temperatures near 50 degrees C the N52I mutation, has a small but significant effect on oxidation state-sensitive structure, in the thermally unfolded protein. Inspection of the high-resolution X-ray, crystallographic structures of iso-2 and N52I iso-2 shows that the effects, of the N52I mutation and oxidation state on native protein stability are, correlated with changes in the mobility of specific polypeptide chain, segments and with altered hydrogen bonding involving a conserved water, molecule. However, there is no clear explanation of oxidation state or, mutation-induced differences in stability of the proteins in terms of, observed changes in structure and mobility of the folded forms of the, proteins alone.
About this Structure
1YTC is a Single protein structure of sequence from Saccharomyces cerevisiae with SO4, TML and HEM as ligands. Full crystallographic information is available from OCA.
Reference
Thermodynamic cycles as probes of structure in unfolded proteins., McGee WA, Rosell FI, Liggins JR, Rodriguez-Ghidarpour S, Luo Y, Chen J, Brayer GD, Mauk AG, Nall BT, Biochemistry. 1996 Feb 13;35(6):1995-2007. PMID:8639684
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