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Effects of buried ionizable amino acids on the reduction potential of recombinant myoglobin
- Source :
- Science (New York, N.Y.). 243(4887)
- Publication Year :
- 1989
-
Abstract
- The temperature dependences of the reduction potentials (E degrees') of wild-type human myoglobin (Mb) and three site-directed mutants have been measured by the use of thin-layer spectroelectrochemistry. Residue Val68, which is in van der Waals contact with the heme in Mb, has been replaced by Glu, Asp, and Asn. The changes in E degrees' and the standard entropy (delta S degrees') and enthalpy (delta H degrees') of reduction in the mutant proteins were determined relative to values for wild type; the change in E degrees' at 25 degrees C was about -200 millivolts for the Glu and Asp mutants, and about -80 millivolts for the Asn mutant. At pH 7.0, reduction of Fe(III) to Fe(II) in the Glu and Asp mutants is accompanied by uptake of a proton by the protein. These studies demonstrate that Mb can tolerate substitution of a buried hydrophobic group by potentially charged and polar residues and that such amino acid replacements can lead to substantial changes in the redox thermodynamics of the protein.
- Subjects :
- Hemeprotein
Stereochemistry
Protein Conformation
Mutant
Glutamic Acid
Heme
chemistry.chemical_compound
Residue (chemistry)
Glutamates
Humans
Site-directed mutagenesis
chemistry.chemical_classification
Aspartic Acid
Multidisciplinary
Myoglobin
Wild type
Valine
Recombinant Proteins
Amino acid
chemistry
Mutation
Thermodynamics
Asparagine
Oxidation-Reduction
Subjects
Details
- ISSN :
- 00368075
- Volume :
- 243
- Issue :
- 4887
- Database :
- OpenAIRE
- Journal :
- Science (New York, N.Y.)
- Accession number :
- edsair.doi.dedup.....c1f7a690b94d41304de5c87c8c058296