Studies of ribosomal diffusion coefficients using laser light-scattering spectroscopy.

Area of Science:

• Molecular Biology
• Biophysics

Background:

• Ribosomes are essential for protein synthesis.
• Understanding ribosome structure and dynamics is crucial for molecular biology.

Purpose of the Study:

• To measure diffusion coefficients and relative scattered intensity of E. coli ribosomes (70S, 50S, 30S).
• To investigate the effects of temperature and Mg(2+) concentration on ribosome behavior.
• To explore ribosome dissociation mechanisms.

Main Methods:

• Optical beating technique to measure diffusion coefficients (D(20,w)).
• Varying temperature (0-40°C) and Mg(2+) concentration.
• Treatment with EDTA and PCMB to induce dissociation.

Main Results:

• Diffusion coefficients for 70S, 50S, and 30S ribosomes were determined at 10 mM Mg(2+).
• Preparative methods significantly influenced diffusion values, suggesting hydration or non-ellipsoidal shapes.
• 70S ribosomes undergo conformational changes before heat-induced dissociation around 30-32°C.
• EDTA treatment caused biphasic dissociation, with Mg(2+) re-addition affecting native conformation recovery.

Conclusions:

• Ribosome subunit expansion occurs upon dissociation.
• Temperature and Mg(2+) concentration are critical factors influencing ribosome stability and conformation.
• Specific chemical treatments like EDTA and PCMB can induce ribosome dissociation through distinct mechanisms.