1YTC

THERMODYNAMIC CYCLES AS PROBES OF STRUCTURE-FUNCTION RELATIONSHIPS IN UNFOLDED PROTEINS

Summary for 1YTC

• Entry DOI: 10.2210/pdb1ytc/pdb
• Descriptor: YEAST ISO-2 CYTOCHROME C, SULFATE ION, HEME C, ... (4 entities in total)
• Functional Keywords: electron transport, heme protein
• Biological source: Saccharomyces cerevisiae (baker's yeast)
• Total number of polymer chains: 1
• Total formula weight: 13179.86

Authors

Luo, Y.,Brayer, G.D. (deposition date: 1995-07-03, release date: 1996-03-08, Last modification date: 2021-11-03)

Primary citation

McGee, W.A.,Rosell, F.I.,Liggins, J.R.,Rodriguez-Ghidarpour, S.,Luo, Y.,Chen, J.,Brayer, G.D.,Mauk, A.G.,Nall, B.T.
Thermodynamic cycles as probes of structure in unfolded proteins.
Biochemistry, 35:1995-2007, 1996

PubMed Abstract: 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.

PubMed: 8639684
DOI: 10.1021/bi951228f

Experimental method

X-RAY DIFFRACTION (1.8 Å)