Effect of hydroxyurea on T4 ribonucleotide reductase

Area of Science:

• Biochemistry
• Enzymology
• Molecular Biology

Background:

• Ribonucleotide reductase is essential for DNA synthesis.
• Phage T4 encodes its own ribonucleotide reductase, distinct from host enzymes.
• Understanding enzyme inhibition is crucial for antiviral and anticancer drug development.

Purpose of the Study:

• To characterize the inhibition of purified phage T4 ribonucleotide reductase by hydroxyurea.
• To compare the sensitivity of T4 and E. coli ribonucleotide reductases to hydroxyurea.
• To investigate the mechanism of hydroxyurea inhibition on T4 ribonucleotide reductase.

Main Methods:

• Purification of phage T4 ribonucleotide reductase to homogeneity.
• Enzyme activity assays to measure substrate reduction.
• Inhibition studies using varying concentrations of hydroxyurea.
• Analysis of substrate specificity and enzyme inactivation.

Main Results:

• Purified phage T4 ribonucleotide reductase catalyzes the reduction of CDP, UDP, ADP, and GDP to their corresponding deoxyribonucleotides.
• The T4 enzyme is significantly more sensitive to hydroxyurea inhibition (50% inhibition at 10 µM) compared to the E. coli enzyme.
• Hydroxyurea completely inhibits the enzyme at high concentrations without differential substrate effects.
• Hydroxyurea treatment does not cause irreversible inactivation of the T4 enzyme or its subunits.

Conclusions:

• Phage T4 ribonucleotide reductase exhibits high sensitivity to hydroxyurea.
• The differential sensitivity to hydroxyurea between T4 and E. coli enzymes may offer insights into enzyme structure-function relationships.
• Hydroxyurea's reversible inhibition suggests potential therapeutic applications targeting viral DNA replication.