Structural insights into the substrate binding of phosphomevalonate kinase from the silkworm, Bombyx mori

Area of Science:

• Biochemistry
• Structural Biology
• Insect Physiology

Background:

• Phosphomevalonate kinase (PMK) is a key enzyme in the juvenile hormone (JH) biosynthesis pathway.
• PMK catalyzes the phosphorylation of mevalonate 5-phosphate to mevalonate 5-diphosphate.
• Understanding PMK's structure and function is vital for insect development and pest control strategies.

Purpose of the Study:

• To elucidate the crystal structure of insect PMK from Bombyx mori (BmPMK).
• To define the substrate and cofactor binding modes of BmPMK.
• To provide a structural basis for understanding the catalytic mechanism and designing PMK inhibitors.

Main Methods:

• X-ray crystallography to determine the 1.60 Å crystal structure of BmPMK.
• Computational simulation, site-directed mutagenesis, and biochemical analysis to study substrate binding.
• Enzyme activity assays to determine optimal pH and temperature.

Main Results:

• The crystal structure of BmPMK reveals a compact α/β conformation with distinct core and lid regions.
• A negatively charged groove at the interface of core and lid regions accommodates substrates.
• Optimal enzyme activity for BmPMK was observed at pH 8.0 and 30°C with mevalonate 5-phosphate.
• Expression profiles and kinetic analyses highlight PMK's critical role in silkworm JH biosynthesis.

Conclusions:

• The determined structure of BmPMK provides crucial insights into insect JH biosynthesis.
• Structural and biochemical data facilitate understanding of PMK's catalytic mechanism.
• Findings offer a foundation for developing targeted PMK inhibitors for pest management.