An x-ray diffraction study of ribosome structure

Area of Science:

• Structural Biology
• Biophysics
• Molecular Biology

Background:

• Ribosomes are complex molecular machines responsible for protein synthesis.
• Understanding the internal structure of ribosomal subunits is crucial for elucidating their function.
• Previous studies have explored ribosomal structure, but detailed internal periodicity remains an area of investigation.

Purpose of the Study:

• To investigate the internal structure and organization of E. coli 70 S ribosomes and their subunits using X-ray diffraction.
• To determine the influence of water content and ionic strength on the structural integrity and periodicity of ribosomal particles.
• To compare the structural properties of intact ribosomes, subunits, and related ribonucleoprotein (RNP) particles.

Main Methods:

• X-ray diffraction analysis of dense gels of E. coli 70 S ribosomes, 50 S subunits, CM-like particles, RNP strands, and free rRNA.
• Comparison of experimental X-ray scattering data with diffraction curves calculated for various model ellipsoidal structures.
• Investigation of structural changes under varying conditions of salt concentration and water content.

Main Results:

• The 50 S ribosomal subunit exhibits a periodic internal structure, forming a lattice with spacings of approximately 42 and 28 Å at a water content of 0.8 g/g.
• This periodic structure is disrupted when the water content drops below 0.2 g/g, but this disruption is reversible.
• CM-like particles show similar internal periodicity to 50 S subunits at high ionic strength (2 M LiCl) but lose this periodicity at low ionic strength.

Conclusions:

• The internal structure of the E. coli 50 S ribosomal subunit is periodic, suggesting a well-defined arrangement of its components.
• Ribosomal structure and periodicity are sensitive to water content and ionic strength, with reversible changes observed.
• The findings provide insights into the structural organization of ribosomal particles and their stability under different environmental conditions.