Solvent effects on horse apomyoglobin dynamics.
Abstract: The effects of the solvent conditions (buffer pH 9, 8, or 7 or buffer pH 6.5 alone or mixed with 3.2% ethanol or 6.2% formamide) on the protein dynamics of horse apomyoglobin were investigated through tryptophan fluorescence quenching, spectra, and decay properties. Raising the pH (which induces discontinuous protein conformation changes) increases the structural fluctuations inside the hydrophobic A, G, and H helix core. Mixed solutions containing either 3.2% ethanol or 6.2% formamide (which redistribute water molecules on the protein surface) produce protein dynamics changes in the vicinity of the two Trp residues, without inducing particular constraints on these very residues. Formamide increases, in the same way, the polarity and the protein flexibility while ethanol reduces both. The present fluorescence work also shows that, whatever the outside solvent, the two Trp residues W7 and W14, embedded in the A, G, and H helix core, are equally and statistically reached by small molecules diffusing inside the protein matrix. Hydrogen-tritium exchange measurements on the protein in mixed solvents reveal that the dynamics of the A, G, and H helix cluster and of the B and E helixes are greatly influenced by the nature of the outside medium. A small amount of formamide in the buffer increases the protein fluctuations while an ethanol-water mixture reduces them. We suggest that the hydratation state of the protein surface could be the relevant parameter of the protein dynamics.
Publication Date: 1998-04-16 PubMed ID: 9485453DOI: 10.1021/bi972236uGoogle Scholar: Lookup
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- Journal Article
Summary
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This study investigates how different solvent conditions impact the protein dynamics of horse apomyoglobin, monitored through tryptophan fluorescence. The research unveils that changes in pH and added substances like ethanol or formamide result in structural changes and can influence the hydration state of the protein, potentially affecting the protein’s overall dynamics.
Research Context and Methodology
- The researchers studied the protein dynamics of horse apomyoglobin under various solvent conditions, including different pH levels (7, 8, and 9) and the addition of other substances like 3.2% ethanol or 6.2% formamide.
- Tryptophan fluorescence quenching, spectra, and decay properties were used as methodologies to monitor the changes in the protein.
Key Findings
- Increasing the pH encourages structural fluctuations within the hydrophobic core of the A, G, and H helix in the protein, a process facilitated by discontinuous protein conformation changes.
- Solutions containing 3.2% ethanol or 6.2% formamide generate alterations in the protein dynamics around the two tryptophan (Trp) residues. However, these substances do not induce specific constraints on these residues.
- Formamide boosts the polarity and flexibility of the protein, whereas ethanol reduces both. This suggests that these substances impact the distribution of water molecules on the protein surface, causing subsequent changes in protein dynamics.
Observations on Trp Residues and Hydrogen-Tritium Exchange
- The study revealed that regardless of the external solvent used, the two Trp residues (W7 and W14), situated within the A, G, H helix core, are uniformly and statistically reached by smaller molecules diffusing into the protein matrix.
- Hydrogen-tritium exchange measurements show that the dynamics of the A, G, and H helix cluster, and of the B and E helices, are significantly influenced by the nature of the external solution. In other words, the presence of certain substances, even in minor quantities, can induce notable effects on the protein dynamics.
- Presence of formamide in the buffer augments protein fluctuations, while an ethanol-water mixture reduces them.
Implications
- The research indicates that the hydration state of the protein surface might be a critical factor in determining the protein dynamics. This finding might have broader implications and contribute to a more nuanced understanding of how solvent conditions affect proteins.
Cite This Article
APA
Haouz A, Glandieres JM, Zentz C, Pin S, Ramstein J, Tauc P, Brochon JC, Alpert B.
(1998).
Solvent effects on horse apomyoglobin dynamics.
Biochemistry, 37(9), 3013-3019.
https://doi.org/10.1021/bi972236u Publication
Researcher Affiliations
- Laboratoire de Biologie Physico-Chimique, Universite Denis Diderot, 2 place Jussieu, 75251 Paris Cedex 05, France.
MeSH Terms
- Animals
- Apoproteins / chemistry
- Horses
- Metmyoglobin / chemistry
- Myocardium / chemistry
- Myoglobin / chemistry
- Protein Conformation
- Solvents
- Spectrometry, Fluorescence
- Tryptophan / chemistry
Citations
This article has been cited 3 times.- Rist W, Rodriguez F, Jørgensen TJ, Mayer MP. Analysis of subsecond protein dynamics by amide hydrogen exchange and mass spectrometry using a quenched-flow setup. Protein Sci 2005 Mar;14(3):626-32.
- Altman M, Lee P, Rich A, Zhang S. Conformational behavior of ionic self-complementary peptides. Protein Sci 2000 Jun;9(6):1095-105.
- Wang ZQ, Wang YH, Qian W, Wang HH, Chunyu LJ, Xie Y, Huang ZX. Methanol-induced unfolding and refolding of cytochrome b5 and its P40V mutant monitored by UV-visible, CD, and fluorescence spectra. J Protein Chem 1999 Jul;18(5):547-55.
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