Intersubunit RNA-protein contacts in pre- and post-translocated E. coli ribosome

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Ribosomes are essential molecular machines responsible for protein synthesis.
• Understanding inter-subunit RNA-protein interactions is crucial for deciphering ribosome function and regulation.
• The dynamic nature of the ribosome during translation involves conformational changes and subunit rearrangements.

Purpose of the Study:

• To identify specific ribosomal proteins involved in inter-subunit RNA-protein contacts within different functional states of the E. coli 70S ribosome.
• To map the locations of these interacting proteins on the ribosomal subunits.
• To investigate how these interactions change during the transition from a tightly coupled state to pre- and post-translocated states.

Main Methods:

• Utilized ultraviolet (UV)-induced cross-linking to identify RNA-protein interactions.
• Analyzed protein-RNA cross-links in three distinct E. coli 70S ribosome states: tight couple, pre-translocated, and post-translocated.
• Localized identified proteins to specific regions on the 30S and 50S ribosomal subunits.

Main Results:

• Identified specific ribosomal proteins (L1, L9, S6, S9/11, S15) that form inter-subunit RNA-protein contacts.
• L1 and L9 proteins interact with 16S RNA, while S6, S9/11, and S15 interact with 23S RNA.
• These 'hinge-joint' proteins are located on the 50S small protuberance and 30S platform, showing a reduction in variable contacts during translocation.

Conclusions:

• The study reveals specific protein-RNA interactions critical for maintaining the integrity of the E. coli 70S ribosome.
• A progressive reduction in inter-subunit RNA-protein contacts occurs during the transition from tight couple to post-translocated states.
• This reduction signifies a gradual loosening or 'opening' of the ribosome, driven by conformational changes linked to functional state alterations.