ATPase strongly bound to higher eukaryotic ribosomes

Area of Science:

• Molecular Biology
• Biochemistry
• Cell Biology

Background:

• Ribosomes are essential cellular machinery responsible for protein synthesis.
• The role of intrinsic ribosomal enzymatic activities, particularly ATPase, in eukaryotic translation is not fully understood.

Purpose of the Study:

• To investigate the intrinsic ATPase activity of 80S ribosomes from higher eukaryotes.
• To elucidate the function and regulation of ribosomal ATPase in nucleotide binding and tRNA interaction.

Main Methods:

• Biochemical assays to measure ATPase activity on isolated 80S ribosomes and subunits.
• Treatment of ribosomes with various concentrations of salts and ethanol to assess enzyme stability.
• Inhibition studies using specific compounds like ammonium metavanadate and adenylylimidodiphosphate.
• Analysis of elongation factor-1 (EF-1) dependent tRNA binding.

Main Results:

• 80S ribosomes exhibit intrinsic ATP and GTP hydrolysis without soluble factors, indicating a stable ribosomal enzyme.
• ATPase activity is associated with both ribosomal subunits and is stimulated by A site occupancy, especially with charged tRNA.
• The enzyme shows broad substrate specificity for NTPs, NDPs, and analogues, preferring ATP.
• Adenylylimidodiphosphate inhibits EF-1 dependent tRNA binding, suggesting ATP hydrolysis is involved in this process.
• Ribosomal ATPase shares similarities with fungal EF-3, and synergistic activity with yeast EF-3 was observed.

Conclusions:

• The 80S ribosomal ATPase is an intrinsic enzymatic activity likely playing a role in the mechanism of tRNA binding to the ribosome.
• This activity may be conserved across different eukaryotic organisms, with potential functional parallels to fungal EF-3.
• Further research could explore the precise catalytic mechanisms and regulatory roles of ribosomal ATPase in translation.