Related Experiment Video
Updated: Jun 9, 2026
11:55
Examining the Conformational Dynamics of Membrane Proteins in situ with Site-directed Fluorescence Labeling
Published on: May 29, 2011
Structural basis for DNA processing and membrane translocation by ComEC in natural transformation
Hisato Hirano1, Naoko Tsuji2, Shinobu Chiba2
1Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
Science (New York, N.Y.)
|April 16, 2026
Summary
Bacterial natural transformation uses ComEC protein to import extracellular DNA. New cryo-EM structures show ComEC processes double-stranded DNA by cleaving one strand and guiding the other into the cell for horizontal gene transfer.
Area of Science:
- Microbiology
- Molecular Biology
- Structural Biology
Background:
- Natural transformation is a key mechanism for bacterial horizontal gene transfer.
- The ComEC protein facilitates DNA uptake but its structure and function were unclear.
Purpose of the Study:
- To elucidate the structure and function of the ComEC protein.
- To provide a structural basis for ComEC's role in natural transformation.
Main Methods:
- Cryo-electron microscopy (cryo-EM) to determine structures of ComEC.
- Biochemical analyses to study ComEC activity.
Main Results:
- Determined cryo-EM structures of ComEC in DNA-free, single-stranded DNA (ssDNA), and double-stranded DNA (dsDNA)-bound states.
- Revealed ComEC cleaves one dsDNA strand extracellularly and translocates the other through a membrane pore.
- Identified a positively charged pore within the membrane domain crucial for DNA translocation.
Conclusions:
- ComEC acts as a DNA processing and translocation machine during natural transformation.
- Structural insights explain ComEC's dual role in DNA cleavage and inner membrane transport.
- Findings provide a mechanistic understanding of horizontal gene transfer in bacteria.
More Related Videos
Related Concept Videos
01:33Bacterial Transformation
In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two pneumonia strains in mice: one pathogenic and one non-pathogenic. Only the pathogenic strain killed host mice.Griffith made an unexpected discovery when he killed the pathogenic strain and mixed its remains with the live, non-pathogenic strain. Not only did the mixture kill host mice, but it also contained living pathogenic bacteria that...
02:13Overview of Transposition and Recombination
Transposons make up a significant part of genomes of various organisms. Therefore, it is believed that transposition played a major evolutionary role in speciation by changing genome sizes and modifying gene expression patterns. For example, in bacteria, transposition can lead to conferring antibiotic resistance. Movement of transposable elements within the genetic pool of pathogenic bacteria can aid in transfer of antibiotic-resistant genetic elements. In eukaryotes, transposons can carry out...
01:26Insertion of Single-pass Transmembrane Proteins in the RER
Integral membrane proteins are proteins adhered to the lipid bilayer of a cell organelle or membrane. They can be of two types: transmembrane integral proteins that span the lipid bilayer and monotopic proteins that are attached to either side of the membrane but do not pass through it.
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
01:29Insertion of Multi-pass Transmembrane Proteins in the RER
The rough ER membrane synthesizes, assembles, and embeds transmembrane proteins in diverse topologies. These proteins function as transporters or channels and can remain in the ER membrane or are sent to the Golgi complex, lysosome, and cell membrane.
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
The multipass transmembrane proteins are the type IV integral membrane proteins with multiple topogenic sequences determining their spatial arrangement in the ER membrane. Nearly all multipass proteins lack a cleavable signal sequence and use...
01:20Mismatch Repair
Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires identifying the new strand and replacing the erroneous bases with correct nucleotides. Mismatch repair is coordinated by many proteins in both prokaryotes and eukaryotes.
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
01:26Transformation
Microbial communities are dynamic environments where cell lysis releases free DNA into the surroundings. Other cells can take up this extracellular DNA through a process known as transformation.When a cell incorporates this foreign DNA into its genome, resulting in genetic modification, the process is known as transformation. Cells capable of this process are termed competent. Competence can be natural, as observed in certain bacteria and archaea, or artificially induced in the...