Folding zones inside the ribosomal exit tunnel

Area of Science:

• Molecular biology
• Protein folding
• Biophysics

Background:

• Membrane protein helicity can form within the ribosome tunnel.
• Factors governing compact structure formation inside the ribosomal tunnel are not well understood.

Purpose of the Study:

• To investigate the determinants of compact structure formation in nascent peptides within the ribosomal tunnel.
• To identify specific regions within the ribosomal tunnel that promote secondary structure formation.

Main Methods:

• Utilized an extended nascent peptide as a molecular tape measure.
• Introduced consecutive polyalanine sequences into different regions of the nascent peptide.
• Calculated free energies for folded and unfolded nascent peptide equilibria.

Main Results:

• Compact structure formation of polyalanine sequences is location-dependent within the ribosomal tunnel.
• Identified distinct zones within the ribosomal exit tunnel that favor secondary structure formation.
• Demonstrated that nascent-chain compaction is influenced by these internal tunnel zones.

Conclusions:

• Specific zones within the ribosomal exit tunnel play a role in nascent-chain compaction.
• Understanding these zones is crucial for deciphering the early stages of membrane protein folding.
• These findings provide insights into the co-translational folding mechanisms of membrane proteins.