Characterization of an Axial Ligand Substitution in Sperm Whale Myoglobin
Of central importance to the study of heme proteins are the effects imposed by axial ligand(s) on the heme structure and, therefore, on the overall activity of the protein. In this study, we confirm and extend the spectroscopic characterization of a mutated sperm whale myoglobin in which the proxima...
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ftutahsudc:oai:digitalcommons.usu.edu:etd-8296 2023-06-11T04:17:05+02:00 Characterization of an Axial Ligand Substitution in Sperm Whale Myoglobin Chen, Michael J. 1995-05-01T07:00:00Z application/pdf https://digitalcommons.usu.edu/etd/7189 https://doi.org/10.26076/c108-5926 https://digitalcommons.usu.edu/context/etd/article/8296/viewcontent/1995_Chen_Michael.pdf unknown DigitalCommons@USU https://digitalcommons.usu.edu/etd/7189 doi:10.26076/c108-5926 https://digitalcommons.usu.edu/context/etd/article/8296/viewcontent/1995_Chen_Michael.pdf Copyright for this work is held by the author. Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owner. Responsibility for any use rests exclusively with the user. For more information contact digitalcommons@usu.edu. All Graduate Theses and Dissertations Axial Ligand Sperm Whale Myoglobin Biochemistry Biophysics and Structural Biology text 1995 ftutahsudc https://doi.org/10.26076/c108-5926 2023-05-04T17:44:43Z Of central importance to the study of heme proteins are the effects imposed by axial ligand(s) on the heme structure and, therefore, on the overall activity of the protein. In this study, we confirm and extend the spectroscopic characterization of a mutated sperm whale myoglobin in which the proximal Histidine is replaced with a Tyrosine residue (MbH93Y). The MbH93Y, as well as wild-type sperm whale myoglobin and horse erythrocyte catalase (HEC), was purified and characterized by optical absorption and x-ray absorption (XAS) spectroscopies. Optical absorption spectra of HEC and the metmyoglobin, cyanometmyoglobin, reduced, oxy, and carbon-monoxy forms of both sperm whale myoglobin (SWMb) and MbH93Y were identical to previously reported values within the respective errors. Extended x-ray absorption fine structure (EXAFS) studies revealed that the proximal bond length in MbH93Y was 2.13 ± 0.03 Å, compared to 2.14 ± 0.02 Å for sperm whale metmyoglobin and 1.90 ± 0.02 Å for catalase. Additionally, the sixth coordination site normally occupied in wild type sperm whale metmyoglobin and in catalase at low temperatures was vacant in MbH93Y, a result corroborated by the optical absorption spectra and cyanogen bromide modification of the distal histidine. Measurements were also made on the cyanide complexes of the three proteins as well, among which, (i) the average iron-to-pyrrole nitrogen bond distance for MbH93Y-CN was 1.96 ± 0.015 Å compared to 2.00 ± 0.015 Å for WT SWMb-CN and HEC-CN and (ii) the proximal bond length in MbH93Y-CN was 2.07 ± 0.02 Å, while that of WT SWMb-CN was 2.10 ± 0.02 Å and that of HEC-CN was found to be 2.12 ± 0.02 Å. Further, upon exposure to 2-molar equivalents of hydrogen peroxide, sperm whale myoglobin formed a Compound II -like spectrum, while the Soret absorbance of MbH93Y was rapidly, significantly, and irreversibly decreased. Furthermore, the dissociation constants for CN binding to MbH93Y were found to be, on average, approximately three orders of magnitude higher than those of ... Text Sperm whale Utah State University: DigitalCommons@USU |
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Utah State University: DigitalCommons@USU |
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topic |
Axial Ligand Sperm Whale Myoglobin Biochemistry Biophysics and Structural Biology |
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Axial Ligand Sperm Whale Myoglobin Biochemistry Biophysics and Structural Biology Chen, Michael J. Characterization of an Axial Ligand Substitution in Sperm Whale Myoglobin |
topic_facet |
Axial Ligand Sperm Whale Myoglobin Biochemistry Biophysics and Structural Biology |
description |
Of central importance to the study of heme proteins are the effects imposed by axial ligand(s) on the heme structure and, therefore, on the overall activity of the protein. In this study, we confirm and extend the spectroscopic characterization of a mutated sperm whale myoglobin in which the proximal Histidine is replaced with a Tyrosine residue (MbH93Y). The MbH93Y, as well as wild-type sperm whale myoglobin and horse erythrocyte catalase (HEC), was purified and characterized by optical absorption and x-ray absorption (XAS) spectroscopies. Optical absorption spectra of HEC and the metmyoglobin, cyanometmyoglobin, reduced, oxy, and carbon-monoxy forms of both sperm whale myoglobin (SWMb) and MbH93Y were identical to previously reported values within the respective errors. Extended x-ray absorption fine structure (EXAFS) studies revealed that the proximal bond length in MbH93Y was 2.13 ± 0.03 Å, compared to 2.14 ± 0.02 Å for sperm whale metmyoglobin and 1.90 ± 0.02 Å for catalase. Additionally, the sixth coordination site normally occupied in wild type sperm whale metmyoglobin and in catalase at low temperatures was vacant in MbH93Y, a result corroborated by the optical absorption spectra and cyanogen bromide modification of the distal histidine. Measurements were also made on the cyanide complexes of the three proteins as well, among which, (i) the average iron-to-pyrrole nitrogen bond distance for MbH93Y-CN was 1.96 ± 0.015 Å compared to 2.00 ± 0.015 Å for WT SWMb-CN and HEC-CN and (ii) the proximal bond length in MbH93Y-CN was 2.07 ± 0.02 Å, while that of WT SWMb-CN was 2.10 ± 0.02 Å and that of HEC-CN was found to be 2.12 ± 0.02 Å. Further, upon exposure to 2-molar equivalents of hydrogen peroxide, sperm whale myoglobin formed a Compound II -like spectrum, while the Soret absorbance of MbH93Y was rapidly, significantly, and irreversibly decreased. Furthermore, the dissociation constants for CN binding to MbH93Y were found to be, on average, approximately three orders of magnitude higher than those of ... |
format |
Text |
author |
Chen, Michael J. |
author_facet |
Chen, Michael J. |
author_sort |
Chen, Michael J. |
title |
Characterization of an Axial Ligand Substitution in Sperm Whale Myoglobin |
title_short |
Characterization of an Axial Ligand Substitution in Sperm Whale Myoglobin |
title_full |
Characterization of an Axial Ligand Substitution in Sperm Whale Myoglobin |
title_fullStr |
Characterization of an Axial Ligand Substitution in Sperm Whale Myoglobin |
title_full_unstemmed |
Characterization of an Axial Ligand Substitution in Sperm Whale Myoglobin |
title_sort |
characterization of an axial ligand substitution in sperm whale myoglobin |
publisher |
DigitalCommons@USU |
publishDate |
1995 |
url |
https://digitalcommons.usu.edu/etd/7189 https://doi.org/10.26076/c108-5926 https://digitalcommons.usu.edu/context/etd/article/8296/viewcontent/1995_Chen_Michael.pdf |
genre |
Sperm whale |
genre_facet |
Sperm whale |
op_source |
All Graduate Theses and Dissertations |
op_relation |
https://digitalcommons.usu.edu/etd/7189 doi:10.26076/c108-5926 https://digitalcommons.usu.edu/context/etd/article/8296/viewcontent/1995_Chen_Michael.pdf |
op_rights |
Copyright for this work is held by the author. Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owner. Responsibility for any use rests exclusively with the user. For more information contact digitalcommons@usu.edu. |
op_doi |
https://doi.org/10.26076/c108-5926 |
_version_ |
1768375908817698816 |