The effect of anions on azide binding to myoglobin: an unusual functional modulation
| Autor: | Claudia Bertonati, Bruno Giardina, Enrico Di Stasio, Andrea Brancaccio, M. Cristina De Rosa |
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| Rok vydání: | 2002 |
| Předmět: |
Anions
Models Molecular inorganic chemicals Azides Stereochemistry Iodates Biophysics Ligands ligandi eterotropici allosteria Biochemistry Dissociation (chemistry) chemistry.chemical_compound Allosteric Regulation Structural Biology mioglobina medicine Animals Horses Binding site Molecular Biology Equilibrium constant Binding Sites molecular modeling Myoglobin Whales Charge density Crystallography Monomer chemistry Spectrophotometry Chlorates Ferric Azide docking molecolare medicine.drug |
| Zdroj: | Biochimica et biophysica acta. Protein structure and molecular enzymology 1594 (2002): 341–352. info:cnr-pdr/source/autori:M. Cristina De Rosa; Claudia Bertonati; Bruno Giardina; Enrico Di Stasio; Andrea Brancaccio/titolo:The effect of anions on azide binding to myoglobin: an unusual functional modulation/doi:/rivista:Biochimica et biophysica acta. Protein structure and molecular enzymology/anno:2002/pagina_da:341/pagina_a:352/intervallo_pagine:341–352/volume:1594 |
| ISSN: | 0167-4838 |
| Popis: | The effect of increasing concentrations of several anions on the azide (N − 3 ) binding properties of sperm whale and horse ferric myoglobin has been studied. Surprisingly, a number of anions may act as heterotropic effectors, decreasing the affinity of myoglobins for N − 3 , in the following order: ClO − 4 =I − >Br − >Cl − and SO 2− 4 , which mirrors the increase in their charge density. The largest effects were measured using ClO − 4 and I − , which produce a 4-fold and 8-fold reduction of the N − 3 binding affinity in horse and sperm whale myoglobins, respectively. A dissociation equilibrium constant ( K d ) ranging from 150 to 250 mM was estimated for ClO − 4 and I − binding to myoglobins. In order to analyse the molecular mechanism producing the reduction of the N − 3 binding affinity to ferric myoglobin, the potential anionic binding sites within ferric myoglobin were investigated by a molecular modelling study using the program Grid. Analysis of the theoretical results suggests two particularly favourable binding sites: the first, next to the distal side of the haem, whose occupancy might alter the electrostatic potential surrounding the bound N − 3 ; the second, involving residues of helices B and G which are far from the haem iron atom, thus implying a long range effect on the bound N − 3 . Based on the evidence that no significant conformational changes are found in the three-dimensional structures of N − 3 -free and N − 3 -bound myoglobin and on previous results on N − 3 binding to ferric myoglobin mutants in CD3 positions, we favour the first hypothesis, suggesting that the functional heterotropic modulation of monomeric myoglobin is mainly depending on a decrease of the positive charge density induced by the binding of anions to the haem distal side. |
| Databáze: | OpenAIRE |
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