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| | {{STRUCTURE_1mni| PDB=1mni | SCENE= }} | | {{STRUCTURE_1mni| PDB=1mni | SCENE= }} |
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| - | '''ALTERATION OF AXIAL COORDINATION BY PROTEIN ENGINEERING IN MYOGLOBIN. BIS-IMIDAZOLE LIGATION IN THE HIS64-->VAL(SLASH)VAL68-->HIS DOUBLE MUTANT'''
| + | ===ALTERATION OF AXIAL COORDINATION BY PROTEIN ENGINEERING IN MYOGLOBIN. BIS-IMIDAZOLE LIGATION IN THE HIS64-->VAL(SLASH)VAL68-->HIS DOUBLE MUTANT=== |
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| - | ==Overview==
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| - | Pig and human myoglobin have been engineered to reverse the positions of the distal histidine and valine (i.e. His64(E7)-->Val and Val68(E11)-->His). Spectroscopic and ligand binding properties have been measured for human and pig H64V/V68H myoglobin, and the structure of the pig H64V/V68H double mutant has been determined to 2.07-A resolution by x-ray crystallography. The crystal structure shows that the N epsilon of His68 is located 2.3 A away from the heme iron, resulting in the formation of a hexacoordinate species. The imidazole plane of His68 is tilted relative to the heme normal; moreover it is not parallel to that of His93, in agreement with our previous proposal (Qin, J., La Mar, G. N., Dou, Y., Admiraal, S. J., and Ikeda-Saito, M. (1994) J. Biol. Chem. 269, 1083-1090). At cryogenic temperatures, the heme iron is in a low spin state, which exhibits a highly anisotropic EPR spectrum (g1 = 3.34, g2 = 2.0, and g3 < 1), quite different from that of the imidazole complex of metmyoglobin. The mean iron-nitrogen distance is 2.01 A for the low spin ferric state as determined by x-ray spectroscopy. The ferrous form of H64V/V68H myoglobin shows an optical spectrum that is similar to that of b-type cytochromes and consistent with the hexacoordinate bisimidazole hemin structure determined by the x-ray crystallography. The double mutation lowers the ferric/ferrous couple midpoint potential from +54 mV of the wild-type protein to -128 mV. Ferrous H64V/V68H myoglobin binds CO and NO to form stable complexes, but its reaction with O2 results in a rapid autooxidation to the ferric species. All of these results demonstrate that the three-dimensional positions of His64 and Val68 in the wild-type myoglobin are as important as the chemical nature of the side chains in facilitating reversible O2 binding and inhibiting autooxidation.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_7608158}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 7608158 is the PubMed ID number. |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Wilkinson, A J.]] | | [[Category: Wilkinson, A J.]] |
| | [[Category: Oxygen storage]] | | [[Category: Oxygen storage]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 01:27:52 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Jul 3 00:28:24 2008'' |
Revision as of 21:28, 2 July 2008
Template:STRUCTURE 1mni
ALTERATION OF AXIAL COORDINATION BY PROTEIN ENGINEERING IN MYOGLOBIN. BIS-IMIDAZOLE LIGATION IN THE HIS64-->VAL(SLASH)VAL68-->HIS DOUBLE MUTANT
Template:ABSTRACT PUBMED 7608158
About this Structure
1MNI is a Single protein structure of sequence from Sus scrofa. Full crystallographic information is available from OCA.
Reference
Alteration of axial coordination by protein engineering in myoglobin. Bisimidazole ligation in the His64-->Val/Val68-->His double mutant., Dou Y, Admiraal SJ, Ikeda-Saito M, Krzywda S, Wilkinson AJ, Li T, Olson JS, Prince RC, Pickering IJ, George GN, J Biol Chem. 1995 Jul 7;270(27):15993-6001. PMID:7608158
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