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Low-temperature-induced structural changes in human lysozyme elucidated by three-dimensional NMR spectroscopy
Hiroyuki Kumeta1, Ai Miura, Yoshihiro Kobashigawa
1Protein Structure Research Group, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), 2-17-2-1, Tsukisamu-Higashi, Toyohira, Sapporo 062-8517, Japan.
Biochemistry
|February 5, 2003
Summary
Human lysozyme structure changes at lower temperatures, with the active site lobe obstructing the cleft. This structural shift explains the reduced lytic activity observed in cold conditions.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Human lysozyme is a key enzyme in innate immunity.
- Understanding enzyme structure-function relationships is crucial for drug development.
Purpose of the Study:
- To investigate the three-dimensional structural changes of human lysozyme at different temperatures.
- To correlate structural alterations with changes in enzymatic activity at low temperatures.
Main Methods:
- Heteronuclear multidimensional NMR spectroscopy was used to determine human lysozyme structures at 35°C and 4°C.
- Lytic activity assays against Micrococcus luteus were performed at varying temperatures.
Main Results:
- Human lysozyme structures at 35°C and 4°C were similar, comprising alpha-helices and beta-strands.
- A significant structural change was observed in the active site lobe, moving to obstruct the active site cleft at lower temperatures.
- Enzyme volume and accessible surface area decreased with temperature, indicating internal cavity shrinkage.
Conclusions:
- Low-temperature-induced structural changes in the active site lobe of human lysozyme likely reduce its lytic activity.
- The observed structural dynamics provide insights into enzyme function under varying thermal conditions.