Related Experiment Video
Updated: Feb 12, 2026
Analysis of Translation Initiation During Stress Conditions by Polysome Profiling
Published on: May 19, 2014
Translation initiation in bacterial polysomes through ribosome loading on a standby site on a highly translated mRNA
Irena Andreeva1, Riccardo Belardinelli1, Marina V Rodnina2
1Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
Abstract:
During translation, consecutive ribosomes load on an mRNA and form a polysome. The first ribosome binds to a single-stranded mRNA region and moves toward the start codon, unwinding potential mRNA structures on the way. In contrast, the following ribosomes can dock at the start codon only when the first ribosome has vacated the initiation site. Here we show that loading of the second ribosome on a natural 38-nt-long 5' untranslated region of lpp mRNA, which codes for the outer membrane lipoprotein from Escherichia coli, takes place before the leading ribosome has moved away from the start codon. The rapid formation of this standby complex depends on the presence of ribosomal proteins S1/S2 in the leading ribosome. The early recruitment of the second ribosome to the standby site before translation by the leading ribosome and the tight coupling between translation elongation by the first ribosome and the accommodation of the second ribosome can contribute to high translational efficiency of the lpp mRNA.
Insights
Consecutive ribosomes form polysomes during translation. Early loading of the second ribosome on lpp mRNA, aided by ribosomal proteins S1/S2, enhances translational efficiency.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Translation involves multiple ribosomes (polysomes) on mRNA.
- Ribosome loading typically requires the start codon to be free.
- The lpp mRNA codes for an essential outer membrane lipoprotein in E. coli.
Purpose of the Study:
- To investigate the mechanism of ribosome loading on lpp mRNA.
- To determine if ribosome recruitment occurs before start codon clearance.
- To identify factors influencing early ribosome loading.
Main Methods:
- Studied ribosome binding to a natural 38-nt 5' untranslated region of lpp mRNA.
- Investigated the role of ribosomal proteins S1/S2 in ribosome recruitment.
- Analyzed the timing of second ribosome loading relative to the first ribosome's position.
Main Results:
- The second ribosome loaded onto lpp mRNA before the first ribosome vacated the start codon.
- This rapid "standby complex" formation was dependent on ribosomal proteins S1/S2.
- Early recruitment and tight coupling of ribosome movement were observed.
Conclusions:
- Early ribosome recruitment to a standby site enhances translational efficiency of lpp mRNA.
- Ribosomal proteins S1/S2 are crucial for this rapid polysome formation.
- This mechanism contributes to high protein output for essential outer membrane proteins.
Related Concept Videos
02:33Initiation of Translation
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
02:33Initiation of Translation
01:31Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of...
01:31Translation
Translation Produces the Building Blocks of Life
Proteins are...
01:44Termination of Translation
02:07Improving Translational Accuracy