Structural determinants increasing flexibility confer cold adaptation in psychrophilic phosphoglycerate kinase

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Background:

• Phosphoglycerate kinase (PGK) is a crucial enzyme in glycolysis, catalyzing ATP production.
• Understanding enzyme adaptations to extreme environments, like psychrophilic conditions, is vital for biochemistry.
• The catalytic mechanism and conformational dynamics of PGK are well-studied, but low-temperature efficiency determinants were unclear.

Purpose of the Study:

• To elucidate the structural basis for high catalytic efficiency of psychrophilic PGK at low temperatures.
• To compare the crystal structures of a psychrophilic PGK with its mesophilic, thermophilic, and hyperthermophilic counterparts.
• To identify specific adaptations contributing to the enzyme's cold-adapted nature.

Main Methods:

• High-resolution X-ray crystallography was employed to determine the crystal structures of Pseudomonas sp. TACII 18 PGK.
• Comparative structural analysis was performed between the psychrophilic PGK and homologous enzymes from organisms with different temperature optima.
• Analysis focused on global and local structural features and their potential impact on enzyme flexibility and activity.

Main Results:

• The study revealed multiple global and local structural adaptations in the cold-adapted PGK.
• These adaptations result in an overall increased flexibility of the enzyme, facilitating better active site accessibility.
• A potential consequence of these adaptations is a more disordered transition state due to the destabilization of certain catalytic residues.

Conclusions:

• Psychrophilic PGK exhibits specific structural modifications that enhance its function at low temperatures.
• Increased flexibility is a key adaptation, improving substrate access but potentially impacting catalytic stability.
• These findings provide insights into the molecular strategies employed by enzymes to function in cold environments.