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Volume and enthalpy profiles of CO rebinding to horse heart myoglobin.
Abstract: Carbon monoxide binding to myoglobin was characterized using the photothermal beam deflection method. The volume and enthalpy changes coupled to CO dissociation were found to be 9.3+/-0.8 mL x mol(-1) and 7.4+/-2.8 kcal x mol(-1), respectively. The corresponding values observed for CO rebinding have the same magnitude but opposite sign: Delta V=-8.6+/-0.9 mL x mol(-1) and Delta H=-5.8+/-2.9 kcal x mol(-1). Ligand rebinding occurs as a single conformational step with a rate constant of 5 x 10(5) M(-1) s(-1) and with activation enthalpy of 7.1+/-0.8 kcal x mol(-1) and activation entropy of -22.4+/-2.8 cal x mol(-1) K(-1). Activation parameters for the ligand binding correspond to the activation parameters previously obtained using the transient absorption methods. Hence, at room temperature the CO binding to Mb can be described as a two-state model and the observed volume contraction occurs during CO-Fe bond formation. Comparing these results with CO dissociation reactions, for which two discrete intermediates were characterized, indicates differences in mechanism by which the protein modulates ligand association and dissociation.
Publication Date: 2003-05-06 PubMed ID: 12733053DOI: 10.1007/s00775-003-0457-4Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The research investigates the specific measurements of volume and enthalpy changes when carbon monoxide (CO) binds and dissociates from a protein called horse heart myoglobin. The study contributes to our understanding of how this protein might influence the binding and releasing of ligands.
Study Method
- Researchers utilized a technique known as the photothermal beam deflection method to analyse the CO binding process to myoglobin, a type of protein found in the muscle tissue of horse hearts.
- The volume and heat changes linked to CO dissociation (i.e., the process where CO seperates from the myoglobin) were specifically measured and recorded.
Significant Findings
- Volume and heat changes (enthalpy) during the CO dissociation process were observed as 9.3+/-0.8 mL x mol(-1) and 7.4+/-2.8 kcal x mol(-1) respectively.
- When CO was reintroduced (a process termed “rebinding”), the researchers found the volume and heat changes had the same magnitude but were in the reverse direction.
Singular Conformational Step and Rate Constant
- Ligand, a substance that forms a complex with a biomolecule, rebinding happened in a single conformational step. This means that the protein changes its shape in one distinct action when binding with the CO ligand.
- It was observed that the rate constant — the speed at which CO binds to the myoglobin — was registered at approximately 5 x 10(5) M(-1) s(-1).
Activation Enthalpy and Entropy
- The study determined the activation enthalpy (a measure of the minimal energy required to start a chemical reaction) for the CO binding process as 7.1+/-0.8 kcal x mol(-1).
- Correspondingly, the activation entropy (which assesses the degree of disorder or randomness in a system) was found to be -22.4+/-2.8 cal x mol(-1) K(-1). Both these measurements matched with data previously obtained with other testing methods.
Final Inferences
- The researchers concluded that at room temperature, the CO binding to myoglobin can be depicted as a two-state model where there’s a volume contraction during the CO-Fe (iron) bond formation.
- When comparing the results with CO dissociation reactions, the researchers flagged discernible variances in the methods or mechanisms by which the protein regulates ligand binding and dissociation.
Cite This Article
APA
Miksovská J, Day JH, Larsen RW.
(2003).
Volume and enthalpy profiles of CO rebinding to horse heart myoglobin.
J Biol Inorg Chem, 8(6), 621-625.
https://doi.org/10.1007/s00775-003-0457-4 Publication
Researcher Affiliations
- Department of Chemistry, University of South Florida, 4202 E Fowler Ave, SCA400, Tampa, FL 33620, USA.
MeSH Terms
- Animals
- Carbon Monoxide / chemistry
- Carbon Monoxide / metabolism
- Energy Transfer
- Horses
- Iron / metabolism
- Ligands
- Myoglobin / metabolism
- Photochemistry / methods
- Protein Binding
- Protein Conformation
- Thermodynamics
References
This article includes 13 references
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Citations
This article has been cited 3 times.- Carlson GM, Fenton AW. What Mutagenesis Can and Cannot Reveal About Allostery. Biophys J 2016 May 10;110(9):1912-23.
- Marcelli A, Abbruzzetti S, Bustamante JP, Feis A, Bonamore A, Boffi A, Gellini C, Salvi PR, Estrin DA, Bruno S, Viappiani C, Foggi P. Following ligand migration pathways from picoseconds to milliseconds in type II truncated hemoglobin from Thermobifida fusca. PLoS One 2012;7(7):e39884.
- Mokdad A, Ang E, Desciak M, Ott C, Vilbert A, Beddow O, Butuc A, Larsen RW, Reynolds MF. Photoacoustic Calorimetry Studies of O(2)-Sensing FixL and (R200, I209) Variants from Sinorhizobium meliloti Reveal Conformational Changes Coupled to Ligand Photodissociation from the Heme-PAS Domain. Biochemistry 2024 Jan 2;63(1):116-127.
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