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Stabilization of the globular structure of ferricytochrome c by chloride in acidic solvents.
Metadata
Journalbiochemistry2.865Date
1975-Nov-18
Publication Type
Research Support, U.S. Gov't, P.H.S.
Journal Article
Volume
1975-Nov-18 / 14 : 5135-40
Author
Stellwagen E , Babul J
DoiPMIDMESH
Animals
Binding Sites
Chlorides
Cytochrome c Group
Horses
Hydrogen-Ion Concentration
Kinetics
Mathematics
Myocardium
Protein Binding
Protein Conformation
Solvents
Spectrophotometry
Viscosity
Abstract
Increasing concentrations of chloride were found to increase the resolution between two visible absorbance spectral transitions associated with acidification of ferricytochrome c. Analysis of a variety of spectral and viscosity measurements indicates that protonation of a single group having an apparent pK of 2.1 +/- 0.2 and an intrinsic pK of about 5.3 displaces the methionine ligand without significantly perturbing the native globular conformation. Analysis of methylated ferricytochrome c suggests that protonation of a carboxylate ion, most likely a heme propionate residue, is responsible for displacement of the methionine ligand. Addition of a proton to a second group having an apparent pK of 1.2 +/- 0.1 displaces the histidine ligand and unfolds the protein from a globular conformation into a random coil. It is most likely that the second protonation occurs on the imidazole ring of the histidine ligand itself. Chloride is proposed to perturb these transitions by ligation in the fifth coordination position of the heme ion. Such ligation stabilizes a globular conformation of ferricytochrome c at pH 0.0 and 25 degrees.
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2.9
Biochemistrybiochemistry
Metadata
LocationUnited States
FromAMER CHEMICAL SOC

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