Structure and location of initiation factor eIF-3 within native small ribosomal subunits from eukaryotes

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Small ribosomal subunits (40SN) are crucial for protein synthesis.
• Understanding the structure and interactions of ribosomal components is key to deciphering translation regulation.
• The eukaryotic initiation factor 3 (eIF-3) plays a vital role in initiating protein synthesis.

Purpose of the Study:

• To investigate the structural features of native 40SN from different sources.
• To determine the location and morphology of the eukaryotic initiation factor 3 (eIF-3) on the 40SN.

Main Methods:

• Electron microscopy was employed for high-resolution imaging.
• Negative staining techniques were used to visualize the ribosomal subunits.
• Native 40SN from rat liver and rabbit reticulocytes were prepared under varying conditions.

Main Results:

• Small ribosomal subunits from rat liver and rabbit reticulocytes exhibited identical structural features.
• The eukaryotic initiation factor 3 (eIF-3) was consistently located on the convex rear side of the 40SN.
• eIF-3 was observed as a flat triangular prism, attached to the ribosomal surface by its base.

Conclusions:

• The binding site and morphology of eIF-3 on the 40SN are conserved across species.
• This structural information provides insights into the mechanism of translation initiation.