Temperature-dependent structural and functional features of a hyperthermostable enzyme using elastic neutron...

Area of Science:

• Biochemistry
• Biophysics
• Enzymology

Background:

• Hyperthermophilic enzymes like endoglucanase from Pyrococcus furiosus exhibit unique stability and activity at high temperatures.
• Understanding the dynamic behavior of these enzymes is crucial for elucidating their functional mechanisms under extreme conditions.

Purpose of the Study:

• To investigate the temperature-dependent dynamic behavior of Pyrococcus furiosus endoglucanase.
• To correlate atomic motions with the enzyme's conformational changes and functional characteristics.
• To elucidate the molecular basis for the onset of biological activity at elevated temperatures.

Main Methods:

• Elastic neutron scattering was employed to probe the atomic motions within the endoglucanase.
• Mean-square displacement of protein atoms was calculated at various temperatures.
• Molecular flexibility and effective force constants were determined.

Main Results:

• A dynamical transition in anharmonic motions was observed around 25°C, correlating with the onset of enzymatic activity.
• Increased temperature weakens intramolecular bonds and decreases protein rigidity, enhancing enzyme activity.
• Beyond optimal temperatures, increased atomic fluctuations indicate heat denaturation.

Conclusions:

• The enzyme's transition to an active conformation involves structurally similar substates in its energy landscape.
• Enzyme activity is directly linked to temperature-induced changes in molecular flexibility and intramolecular bond strength.
• Elastic neutron scattering provides insights into the dynamic mechanisms underlying hyperthermophilic enzyme function and denaturation.