Crystallographic, Molecular Modeling, and Biophysical Characterization of the Valineβ67 (E11) → Threonine Variant of Hemoglobin
| Autor: | Michael Karavitis, Igor Pechik, Gary L. Gilliland, Krzysztof Fidelis, Clara Fronticelli, William S. Brinigar, Xinhua Ji, John Moult |
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| Rok vydání: | 1996 |
| Předmět: |
Models
Molecular Threonine Protein Folding Molecular model Protein Conformation Stereochemistry Biophysics Heme In Vitro Techniques Crystallography X-Ray Nitric Oxide Biochemistry Biophysical Phenomena Hemoglobins chemistry.chemical_compound Protein structure Electrochemistry Side chain Humans Point Mutation Hydrogen bond Chemistry Oxygen transport Genetic Variation Hemoglobin A Recombinant Proteins Crystallography Carboxyhemoglobin Myoglobin Oxidation-Reduction Protein Processing Post-Translational |
| Zdroj: | Biochemistry. 35:1935-1945 |
| ISSN: | 1520-4995 0006-2960 |
| Popis: | The crystal structure of the mutant deoxyhemoglobin in which the beta-globin Val67(E11) has been replaced with threonine [Fronticelli et al. (1993) Biochemistry 32, 1235-1242] has been determined at 2.2 A resolution. Prior to the crystal structure determination, molecular modeling indicated that the Thr67(E11) side chain hydroxyl group in the distal beta-heme pocket forms a hydrogen bond with the backbone carbonyl of His63(E7) and is within hydrogen-bonding distance of the N delta of His63(E7). The mutant crystal structure indicates only small changes in conformation in the vicinity of the E11 mutation confirming the molecular modeling predictions. Comparison of the structures of the mutant beta-subunits and recombinant porcine myoglobin with the identical mutation [Cameron et al. (1993) Biochemistry 32, 13061-13070] indicates similar conformations of residues in the distal heme pocket, but there is no water molecule associated with either of the threonines of the beta-subunits. The introduction of threonine into the distal heme pocket, despite having only small perturbations in the local structure, has a marked affect on the interaction with ligands. In the oxy derivative there is a 2-fold decrease in O2 affinity [Fronticelli et al. (1993) Biochemistry 32, 1235-1242], and the rate of autoxidation is increased by 2 orders of magnitude. In the CO derivative the IR spectrum shows modifications with respect to that of normal human hemoglobin, suggesting the presence of multiple CO conformers. In the nitrosyl derivative an interaction with the O gamma atom of Thr67(E11) is probably responsible for the 10-fold increase in the rate of NO release from the beta-subunits. In the aquomet derivative there is a 6-fold decrease in the rate of hemin dissociation suggesting an interaction of the Fe-coordinated water with the O gamma of Thr67(E11). |
| Databáze: | OpenAIRE |
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