Publication Date:
1989-01-06
Description:
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 Residue Val68, which is in van der Waals contact with the heme in Mb, has been replaced by Glu, Asp, and Asn.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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Varadarajan, R -- Zewert, T E -- Gray, H B -- Boxer, S G -- DK 19038/DK/NIDDK NIH HHS/ -- GM 27738/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 1989 Jan 6;243(4887):69-72.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Stanford University, CA 94305.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2563171" target="_blank"〉PubMed〈/a〉
Keywords:
Asparagine
;
Aspartic Acid
;
Glutamates
;
Glutamic Acid
;
Heme/metabolism
;
Humans
;
Mutation
;
Myoglobin/*metabolism
;
Oxidation-Reduction
;
Protein Conformation
;
Recombinant Proteins/*metabolism
;
Thermodynamics
;
Valine
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
