1mgn: Difference between revisions

Revision as of 00:59, 3 May 2008

HIS64(E7)-> TYR APOMYOGLOBIN AS A REAGENT FOR MEASURING RATES OF HEMIN DISSOCIATION

OverviewOverview

To develop an assay for hemin dissociation, His64(E7) was replaced by Tyr in sperm whale myoglobin producing a holoprotein with a distinct green color due to an intense absorption band at 600 nm. Val68(E11) was replaced by Phe in the same protein to increase its stability. When excess Tyr64-Val68 apoglobin is mixed with either metmyoglobin or methemoglobin, the solution turns from brown to green, and the absorbance changes can be used to measure complete time courses for hemin dissociation from either holoprotein. This assay has been used to measure rates of hemin dissociation from native metmyoglobin, four myoglobin mutants (Ala64(E7), Ala68(E11), Phe68(E11), and Glu45(CD3)), native methemoglobin, valence hybrid hemoglobins, and two mutant hemoglobins ((alpha(Gly-E7)beta(native))2, and (alpha(native)beta(Gly-E7))2). Two kinetic phases were observed for hemin dissociation from native human hemoglobin at pH 7.0 and 37 degrees C. Valence and mutant hybrid hemoglobins were used to assign the faster phase (k = 7.8 +/- 2.0 h-1) to hemin dissociation from ferric beta subunits and the slower (k = 0.6 +/- 0.15 h-1) to dissociation from alpha subunits. The corresponding rate for wild-type metmyoglobin is 0.007 +/- 0.004 h-1.

About this StructureAbout this Structure

1MGN is a Single protein structure of sequence from Physeter catodon. Full crystallographic information is available from OCA.

ReferenceReference

His64(E7)-->Tyr apomyoglobin as a reagent for measuring rates of hemin dissociation., Hargrove MS, Singleton EW, Quillin ML, Ortiz LA, Phillips GN Jr, Olson JS, Mathews AJ, J Biol Chem. 1994 Feb 11;269(6):4207-14. PMID:8307983 Page seeded by OCA on Sat May 3 00:59:54 2008

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OCA

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-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Mar 30 22:15:49 2008''