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Effects of buried ionizable amino acids on the reduction potential of recombinant myoglobin

Varadarajan, Raghavan and Zewert, Thomas E. and Gray, Harry B. and Boxer, Steven G. (1989) Effects of buried ionizable amino acids on the reduction potential of recombinant myoglobin. Science, 243 (4887). pp. 69-72. ISSN 0036-8075. http://resolver.caltech.edu/CaltechAUTHORS:20150128-121300760

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Abstract

The temperature dependences of the reduction potentials (E°') 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 Residue Val68, which is in van der Waals contact with the heme in Mb, has been replaced by Glu, Asp, and Asn.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 (ΔS°') and enthalpy (ΔH°') of reduction in the mutant proteins were determined relative to values for wild type; the change in E°' at 25 °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.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1126/science.2563171DOIArticle
http://www.sciencemag.org/content/243/4887/69PublisherArticle
http://www.jstor.org/stable/1703177JSTORArticle
Additional Information:© 1989 American Association for the Advancement of Science. 1 September 1988; Accepted 1 November 1988. We thank W. R. Ellis, Jr., and H. C. Andersen for helpful discussions. Supported in part by NIH grant GM 27738 (S.G.B.), a Presidential Young Investigator Award to S.G.B. (matching funds from Monsanto Corp.), and NIH grant DK 19038 (H.B.G.). This is contribution No. 7853 from the Arthur Amos Noyes Laboratory.
Funders:
Funding AgencyGrant Number
NIHGM 27739
NSFUNSPECIFIED
NIHDK 19038
Monsanto CorporationUNSPECIFIED
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Arthur Amos Noyes Laboratory of Chemical Physics7853
Record Number:CaltechAUTHORS:20150128-121300760
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20150128-121300760
Official Citation:Varadarajan, R., Zewert, T., Gray, H., & Boxer, S. (1989). Effects of buried ionizable amino acids on the reduction potential of recombinant myoglobin. Science, 243(4887), 69-72. doi: 10.1126/science.2563171
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:54187
Collection:CaltechAUTHORS
Deposited By: Joanne McCole
Deposited On:28 Jan 2015 20:52
Last Modified:28 Jan 2015 20:52

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