Oxidation of deoxy myoglobin by [Fe(CN)6]3-.
The ability of myoglobin (Mb) to reversibly bind O2 and other ligands has been well characterized. Mb also participates with a variety of redox metals to form metmyoglobin (metMb). By using an anaerobic stopped-flow device we have measured outer-sphere oxidation by [Fe(CN)6]3 of native sperm whale myoglobin, recombinant wild-type Mb, and a series of mutant Mb proteins in which the distal His-64 was changed to Gly, Phe, Leu or Val. Second-order rate constants for oxidation of mutant proteins are 10-15 times greater than for recombinant or native (kox approximately 10(6) M-1 s-1). We attribute the reduced rate of oxidation of wild-type protein to a higher reorganization energy imposed by the presence of the unique water/His-64/heme interaction, which is absent in the mutant proteins.
Dunn
C J
CJ
Department of Biology, University of California at San Diego 92093-0368, USA.
Rohlfs
R J
RJ
Fee
J A
JA
Saltman
P
P
D019943:Amino Acid Substitution; D000818:Animals; D005292:Ferricyanides / Q000737:chemistry / Q000378:metabolism*; D006639:Histidine; D009211:Myoglobin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013053:Spectrophotometry / Q000379:methods; D014907:Whales
D005292:Ferricyanides; D009211:Myoglobin; D011994:Recombinant Proteins; C055547:deoxymyoglobin; C007931:hexacyanoferrate III; D006639:Histidine