Related Experiment Video
Updated: Jun 26, 2026
08:49
Peering at Brain Polysomes with Atomic Force Microscopy
Published on: March 16, 2016
The native 3D organization of bacterial polysomes
Florian Brandt1, Stephanie A Etchells, Julio O Ortiz
1Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, Martinsried 82152, Germany.
Cell
|January 27, 2009
Summary
Researchers mapped bacterial ribosome 3D organization in polysomes using cryoelectron tomography. Ribosomes form staggered arrangements along mRNA, optimizing nascent polypeptide chain folding and preventing aggregation.
Area of Science:
- Molecular Biology
- Structural Biology
- Biophysics
Background:
- Recent advances have elucidated bacterial ribosome structure.
- The 3D organization of ribosomes within polysomes remains poorly understood.
Purpose of the Study:
- To investigate the three-dimensional arrangement of bacterial 70S ribosomes in polysomes.
- To understand how ribosome organization impacts nascent polypeptide chain folding.
Main Methods:
- Cryoelectron tomography was used to visualize ribosomes in vitrified bacterial translation extracts and E. coli lysates.
- A template-matching approach was employed to map the positions and orientations of 70S ribosomes.
Main Results:
- Polysomes exhibit densely packed ribosomes with preferred orientations.
- A staggered or pseudohelical organization of ribosomes along the mRNA was observed.
- The mRNA is sequestered internally, with accessible tRNA entry and polypeptide exit sites facing the cytosol.
Conclusions:
- This arrangement maximizes distance between nascent chains, reducing aggregation.
- The observed polysome structure facilitates productive folding of newly synthesized proteins.
Related Concept Videos
00:43Bacterial RNA Polymerase
Unlike eukaryotes, bacteria use a single RNA Polymerase (RNAP) to transcribe all genes. The different subunits of bacterial RNAPhave distinct functions. The multisubunit structure of the bacterial RNAP helps the enzyme to maintain catalytic function, facilitate assembly, interact with DNA and RNA, and self-regulate its activity.
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...
00:43Bacterial RNA Polymerase
Unlike eukaryotes, bacteria use a single RNA Polymerase (RNAP) to transcribe all genes. The different subunits of bacterial RNAPhave distinct functions. The multisubunit structure of the bacterial RNAP helps the enzyme to maintain catalytic function, facilitate assembly, interact with DNA and RNA, and self-regulate its activity.
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...
In most genes, the transcription site is a single base present upstream of the coding sequence. Though RNAP is a catalytically efficient enzyme, it does not recognize...
01:29Coordination of Gene Expression Processes in Bacteria
The DNA replication, transcription, and translation processes are intricately coupled in bacteria, allowing efficient gene expression and rapid protein synthesis. While this physical and functional coordination is advantageous, it introduces challenges that bacteria overcome through specific regulatory mechanisms.Coupling of Replication, Transcription, and TranslationThe coupling of replication, transcription, and translation is a hallmark of bacterial gene expression. As the replisome unwinds...
01:29Cytoskeletal Proteins in Bacteria
Bacterial cells were initially considered simple, randomly organized structures lacking a cytoskeleton. However, the discovery of cytoskeleton homologs in bacteria led to the change of this opinion. Bacterial cytoskeletal filaments regulate the cell shape, cell polarity, cell division, and partitioning of plasmids during cell division. It was later discovered that bacterial cytoskeletal proteins, mainly actin and tubulin homologs, are diverse compared to their eukaryotic counterparts. On the...
01:28Prokaryotic Gene Structure and Organization
Prokaryotic genomes exhibit a streamlined organization of coding and non-coding regions essential for gene expression and protein synthesis. While coding regions contain the genetic instructions for proteins or functional RNAs, non-coding regions regulate the precise transcription and translation of these genes.Coding Regions: Proteins and RNAsThe primary coding regions, known as structural genes, include sequences transcribed into messenger RNA (mRNA) and ultimately translated into...
01:24Nucleoid
The nucleoid represents a structurally and functionally distinct region within prokaryotic cells, where the cell's DNA and associated proteins are housed. Unlike eukaryotic cells, prokaryotes lack a membrane-bound nucleus, and the nucleoid facilitates the organization and accessibility of the genetic material within this constraint. The DNA in most bacteria and archaea exists as a single, circular, double-stranded molecule that is highly compacted through supercoiling and interactions with...