The proximal and distal pockets of the H93G myoglobin cavity mutant bind identical ligands with different affinities: Quantitative analysis of imidazole and pyridine binding
His93Gly sperm whale myoglobin (H93G Mb) has the proximal histidine ligand removed to create a cavity for exogenous ligand binding, making it a versatile template for the preparation of model heme complexes. In this study, we have measured the first and second ligand binding affinities of imidazole...
Main Authors: | , , |
---|---|
Language: | English |
Published: |
Spectroscopy
2008
|
Subjects: | |
Online Access: | https://doi.org/10.3233/SPE-2008-0330 |
id |
fthindawi:oai:hindawi.com:10.3233/SPE-2008-0330 |
---|---|
record_format |
openpolar |
spelling |
fthindawi:oai:hindawi.com:10.3233/SPE-2008-0330 2023-05-15T18:26:49+02:00 The proximal and distal pockets of the H93G myoglobin cavity mutant bind identical ligands with different affinities: Quantitative analysis of imidazole and pyridine binding Jing Du Masanori Sono John H. Dawson 2008 https://doi.org/10.3233/SPE-2008-0330 en eng Spectroscopy https://doi.org/10.3233/SPE-2008-0330 Copyright © 2008 Hindawi Publishing Corporation. 2008 fthindawi https://doi.org/10.3233/SPE-2008-0330 2019-05-26T02:27:07Z His93Gly sperm whale myoglobin (H93G Mb) has the proximal histidine ligand removed to create a cavity for exogenous ligand binding, making it a versatile template for the preparation of model heme complexes. In this study, we have measured the first and second ligand binding affinities of imidazole and pyridine to form mono- and bis-ligated ferric and ferrous H93G Mb complexes. Electronic absorption spectroscopy has been utilized to determine the binding affinities for the proximal (Kd1, first ligand) and distal (Kd2, second ligand) pockets of H93G Mb. Magnetic circular dichroism spectroscopy has been used to confirm the identity of the complexes. The binding affinities for the first ligand are one hundred- to one thousand-fold higher than those for the second ligand (Kd1 « Kd2) for the same exogenous ligand. This is entirely opposite to what is seen with free heme in organic solvents where Kd1 » Kd2. Thus, the proximal pocket is the high affinity binding site. The lower affinity for the distal pocket can be attributed to steric hindrance from the distal histidine. This report provides quantitative evidence for differential ligand binding affinities of the proximal and distal pockets of H93G Mb, a unique property that facilitates generation of heme iron derivatives not easily prepared with other heme model systems. Other/Unknown Material Sperm whale Hindawi Publishing Corporation |
institution |
Open Polar |
collection |
Hindawi Publishing Corporation |
op_collection_id |
fthindawi |
language |
English |
description |
His93Gly sperm whale myoglobin (H93G Mb) has the proximal histidine ligand removed to create a cavity for exogenous ligand binding, making it a versatile template for the preparation of model heme complexes. In this study, we have measured the first and second ligand binding affinities of imidazole and pyridine to form mono- and bis-ligated ferric and ferrous H93G Mb complexes. Electronic absorption spectroscopy has been utilized to determine the binding affinities for the proximal (Kd1, first ligand) and distal (Kd2, second ligand) pockets of H93G Mb. Magnetic circular dichroism spectroscopy has been used to confirm the identity of the complexes. The binding affinities for the first ligand are one hundred- to one thousand-fold higher than those for the second ligand (Kd1 « Kd2) for the same exogenous ligand. This is entirely opposite to what is seen with free heme in organic solvents where Kd1 » Kd2. Thus, the proximal pocket is the high affinity binding site. The lower affinity for the distal pocket can be attributed to steric hindrance from the distal histidine. This report provides quantitative evidence for differential ligand binding affinities of the proximal and distal pockets of H93G Mb, a unique property that facilitates generation of heme iron derivatives not easily prepared with other heme model systems. |
author |
Jing Du Masanori Sono John H. Dawson |
spellingShingle |
Jing Du Masanori Sono John H. Dawson The proximal and distal pockets of the H93G myoglobin cavity mutant bind identical ligands with different affinities: Quantitative analysis of imidazole and pyridine binding |
author_facet |
Jing Du Masanori Sono John H. Dawson |
author_sort |
Jing Du |
title |
The proximal and distal pockets of the H93G myoglobin cavity mutant bind identical ligands with different affinities: Quantitative analysis of imidazole and pyridine binding |
title_short |
The proximal and distal pockets of the H93G myoglobin cavity mutant bind identical ligands with different affinities: Quantitative analysis of imidazole and pyridine binding |
title_full |
The proximal and distal pockets of the H93G myoglobin cavity mutant bind identical ligands with different affinities: Quantitative analysis of imidazole and pyridine binding |
title_fullStr |
The proximal and distal pockets of the H93G myoglobin cavity mutant bind identical ligands with different affinities: Quantitative analysis of imidazole and pyridine binding |
title_full_unstemmed |
The proximal and distal pockets of the H93G myoglobin cavity mutant bind identical ligands with different affinities: Quantitative analysis of imidazole and pyridine binding |
title_sort |
proximal and distal pockets of the h93g myoglobin cavity mutant bind identical ligands with different affinities: quantitative analysis of imidazole and pyridine binding |
publisher |
Spectroscopy |
publishDate |
2008 |
url |
https://doi.org/10.3233/SPE-2008-0330 |
genre |
Sperm whale |
genre_facet |
Sperm whale |
op_relation |
https://doi.org/10.3233/SPE-2008-0330 |
op_rights |
Copyright © 2008 Hindawi Publishing Corporation. |
op_doi |
https://doi.org/10.3233/SPE-2008-0330 |
_version_ |
1766208783562833920 |