Stability of equine lysozyme. I. Thermal unfolding behaviour.
Abstract: The thermal denaturation of Ca(2+)- and apo-forms of equine lysozyme was followed by using far and near UV circular dichroism and intrinsic fluorescence methods. The difference found between the temperature dependence of the ellipticity at 222 nm and 287 nm, which show two stages in the thermal transition, and those at 228 nm and 294 nm, which indicate only one stage over a wide range of temperatures reflects that different subdivisions of the protein molecule are characterized by a different stability, cooperativity and pathway of denaturation. The first transition, reflected in the increase of the ellipticity at 222 nm and 287 nm, coincides with the transition detected by fluorescence and occurs at 30-50 degrees C for the apo-form and at 50-60 degrees C for the Ca(2+)-form of lysozyme. It seems to correlate with the transfer of some tryptophan residues to a more hydrophobic environment and with a local rearrangement of the tertiary and secondary structures. The unfolding transition detected by the decrease of the ellipticity at all wavelengths occurs nearly in the same temperature region for the apo- and Ca(2+)-forms, i.e. 50-80 degrees C and 55-80 degrees C, respectively. The presence of a Ca(2+)-binding loop in equine lysozyme may be partly responsible for the drastic destabilization of its structure as a whole both in the presence but especially in the absence of Ca2+ in comparison with hen and human lysozymes.
Publication Date: 1991-11-01 PubMed ID: 1773011DOI: 10.1016/0301-4622(91)80018-mGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research examines the behavior of equine lysozyme, a protein found in horses, when it is subjected to varying temperatures. It utilizes UV circular dichroism and intrinsic fluorescence to observe changes in the structure of the protein, discovering that different parts of the molecule have varying levels of stability, cooperativity, and denaturation paths.
Understanding the Study
- Lysozymes are enzymes that are a crucial part of an organism’s immune system. In this context, equine lysozyme refers to the variant found in horses. The study is primarily concerned with the thermal behavior of two specific variants of equine lysozyme, apo-forms and Ca(2+)-forms, and how heat influences their structural stability.
- The researchers used analytical methods such as far and near UV circular dichroism and intrinsic fluorescence to track the thermal denaturation or unfolding of these proteins.
- Denaturation is a process where proteins lose their structure due to external stressors like heat or chemicals. The stability of a protein, in these terms, refers to how well it maintains its structure under these stressors.
Results and Observations
- Two different measurement wavelengths showed two separate stages of thermal transition, while another set of wavelengths indicated only one, hinting that the molecule displayed differences in stability and denaturation paths within its own structure.
- The data indicated that the first transition stage of the protein’s unfolding was related to the environment of tryptophan residues in the protein structure becoming more hydrophobic, and there being a local reorganisation of the tertiary and secondary structures.
- The second stage of unfolding, identifiable by decreases in ellipticity across all examined wavelengths, occurred roughly in the same temperature range for both apo- and Ca(2+)-forms.
- The presence of a Ca2+-binding loop in equine lysozyme was found to potentially contribute to a significant destabilization of its structure, more pronouncedly so in the absence of Ca2+ ions in comparison to hen and human lysozymes.
Significance of the Research
- This study provides a more detailed insight into the behaviour of equine lysozymes under thermal stress, adding knowledge about how different forms of this protein respond to temperature changes.
- Understanding these behaviors can help in areas such as protein engineering and the creation of temperature-responsive biomaterials.
- These findings can also help in understanding the general functional mechanisms of lysozymes in different species, such as horses, hens, and humans, aiding in comparative protein studies.
Cite This Article
APA
Morozova L, Haezebrouck P, Van Cauwelaert F.
(1991).
Stability of equine lysozyme. I. Thermal unfolding behaviour.
Biophys Chem, 41(2), 185-191.
https://doi.org/10.1016/0301-4622(91)80018-m Publication
Researcher Affiliations
- Interdisciplinair Research Center, K.U. Leuven Campus Kortrijk, Belgium.
MeSH Terms
- Animals
- Circular Dichroism
- Fluorescence Polarization
- Horses
- Hot Temperature
- Milk / enzymology
- Muramidase / chemistry
- Protein Conformation
- Protein Denaturation
- Spectrophotometry, Ultraviolet
Citations
This article has been cited 3 times.- Xie L, Chou SG, Pande A, Pande J, Zhang J, Dresselhaus MS, Kong J, Liu Z. Single-Walled Carbon Nanotubes Probing the Denaturation of Lysozyme. J Phys Chem C Nanomater Interfaces 2010 May 6;114(17):7717-7720.
- Malik A, Alsenaidy MA. MERS-CoV papain-like protease (PL(pro)): expression, purification, and spectroscopic/thermodynamic characterization. 3 Biotech 2017 Jun;7(2):100.
- James NG, Ross JA, Stefl M, Jameson DM. Applications of phasor plots to in vitro protein studies. Anal Biochem 2011 Mar 1;410(1):70-6.
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