1997
DOI: 10.1007/s007750050165
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Myoglobin models and steric origins of the discrimination between O2 and CO

Abstract: Synthetic models of the myoglobin active site have provided much insight into factors that affect CO and O 2 binding in the proteins. "Capped" and "pocket" metal porphyrin systems have been developed to probe how steric factors affect ligand binding and ultimately to elucidate important aspects of the mechanism of CO discrimination in the proteins. These model porphyrins are among the most thoroughly characterized systems to date. From the twenty-one known crystal structures, analysis of the types of distortio… Show more

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Cited by 47 publications
(46 citation statements)
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“…For example, both H64L and V68I MbCO show Fe-C-O angles equal to F1657, even though the affinities of these mutants for CO differ by a factor of 500 (Table 1). Although the current controversy between Fe-C-O angles measured spectroscopically and those determined by crystallography remains unresolved [47][48][49], this problem appears to be less important than originally thought since CO affinity cannot be predicted by this angle. This latter view is supported by recent theoretical calculations which indicate that the free energy required for bending FeCO is not as great as originally thought [50,51].…”
Section: Co Affinity and The Fe-c-o Bond Anglementioning
confidence: 90%
“…For example, both H64L and V68I MbCO show Fe-C-O angles equal to F1657, even though the affinities of these mutants for CO differ by a factor of 500 (Table 1). Although the current controversy between Fe-C-O angles measured spectroscopically and those determined by crystallography remains unresolved [47][48][49], this problem appears to be less important than originally thought since CO affinity cannot be predicted by this angle. This latter view is supported by recent theoretical calculations which indicate that the free energy required for bending FeCO is not as great as originally thought [50,51].…”
Section: Co Affinity and The Fe-c-o Bond Anglementioning
confidence: 90%
“…Few biomolecular issues have generated as much controversy as that of the deformability of the CO ligand when bound to heme proteins [1][2][3][4][5][6]. A central point of this controversy is the mechanism of discrimination between O 2 and CO by respiratory heme proteins.…”
Section: Introductionmentioning
confidence: 99%
“…1). The study of superstructured porphyrins has made it clear that steric forces can strongly discriminate between CO and O 2 [17], but their relative importance in heme proteins has been a contentious issue [1][2][3][4][5][6].…”
Section: Introductionmentioning
confidence: 99%
“…Instead it appears that two helices that hold the heme in place, helices E and F, move slightly away from one another giving rise to the longer Val68 (E11) to CO distances observed in the MbCO structure. Since O 2 binds at an angle to the heme normal [15], a smaller distortion of the polypeptide would be required to accommodate it; hence, the steric barrier for O 2 binding should be lower [5]. These highresolution room temperature structures not only provide insight into the mechanism of CO inhibition, but also suggest an explanation for why mutants of myoglobin with a smaller distal side chain at the histidine E7 position have the same linear Fe-C-O geometry as the wild type protein [16].…”
Section: Myoglobinsmentioning
confidence: 99%
“…Most globins also have a distal histidine (E7), lining the O 2 -binding pocket that has been implicated in enhancing O 2 binding by electrostatic interactions, and by sterically hindering the binding of other ligands such as CO (Fig. 1) [5].…”
Section: Globinsmentioning
confidence: 99%