A frozen 3D view shows how bacteria make, move, and shape proteins
cryo-electron tomography
A method that makes three-dimensional views of frozen cells.
ribosome
A cell machine that builds proteins.
Sec-translocon
A protein channel in the cell membrane.
What happened
A team led by Julia Mahamid at the European Molecular Biology Laboratory (EMBL), a research organization, studied how bacterial cells coordinate protein production and transport. The findings appeared in two papers in Cell. The work used Mycoplasma pneumoniae, the bacterium chosen as a relatively simple cell model.
Many cell studies examine one molecular machine at a time. These researchers instead asked how different machines meet and cooperate. Their result is not a movie of a whole cell. It is a detailed set of structural views that connects several steps.
How the researchers looked inside
The team used cryo-electron tomography, or cryo-ET. They flash-froze cells and reconstructed three-dimensional maps from them. This allowed the researchers to examine molecular machines inside cells. One study mapped and counted ribosomes in different functional states across hundreds of individual cells.
Protein production was linked
Ribosomes make proteins. Before that, the cell copies information from DNA into messenger RNA. The cell then uses that message to build a protein. The researchers observed several complexes that directly connect these two processes, called transcription and translation.
The structures provide evidence for long-proposed supercomplexes. They also suggest ways the cell may regulate the two processes together. Some ribosome subunits remained attached to the cell membrane even when they were not making proteins. The team suggests they may detach when conditions allow a new round of production. Similar behavior was reported in mammalian cells decades ago, but that does not prove every cell uses the same mechanism.
Transport and folding met at the membrane
A second study started with an unknown structure at the cell surface. The researchers combined cryo-ET with proteomics and computational protein-structure predictions. They found the Sec-translocon, a protein channel in the membrane. It helps move newly made proteins out of the cell or into the membrane.
The structure also contained three previously unknown proteins. These proteins appear to help transported proteins fold into their working shapes. The images showed newly translated proteins beginning to move through the membrane. They also linked that movement with a newly discovered folding system outside the cell.
Why this matters
The main advance is a change in scale. Scientists can now study molecular machines as members of a working community. That matters because protein production, transport, and folding are connected tasks. Looking at them together may reveal controls that isolated structures hide.
The bacterium is relatively simple. That makes it a useful place to develop the method. The researchers describe both studies as proof-of-concept work. The approach could later be applied to more complex organisms.
What remains unknown
The images show structures and different states. They do not answer every timing question. Researchers still need to determine exactly when ribosome parts leave the membrane. They also need to explain how each new protein supports folding. Similar patterns in mammalian cells are suggestive, not final proof of a universal process.
What to watch next
The next step is to use the method in other cells and organisms. Researchers will test which connections are widely shared. They will also ask how molecular communities change when cells grow, respond to stress, or become diseased.
Source: Phys.org report
3D pictures show bacteria making and moving proteins
📰 Full story: A frozen 3D view shows how bacteria make, move, and shape proteins
Scientists saw several cell jobs working together.
Mycoplasma pneumoniae
The bacterium used as the study model.
ribosome
A cell machine that builds proteins.
Sec-translocon
A protein channel that moves new proteins.
💡 The gist
- Scientists made detailed 3D pictures inside bacterial cells.
- Ribosomes made proteins near the cell membrane.
- Other machinery helped move and shape those proteins.
Researchers studied Mycoplasma pneumoniae, the bacterium used in the study. They froze the cells quickly. Then they used cryo-electron tomography. This method makes 3D views of very small structures.
The researchers studied hundreds of cells. They counted ribosomes in different working states. A ribosome is a machine that builds proteins. Some ribosome parts stayed near the membrane while idle. The researchers think they may leave when production starts again.
The study also showed two connected steps. First, the cell copies DNA information into a message. This step is called transcription. Next, a ribosome reads the message and builds a protein. This step is called translation. Several complexes connected these steps inside the cell. That connection may help the cell control protein production.
The new pictures also showed transport at the membrane. The Sec-translocon is a protein channel in the membrane. It can move new proteins outside the cell. It can also place some proteins into the membrane. Three previously unknown proteins were part of the same machinery. They appear to help new proteins fold into the right shapes.
Shape matters because proteins need the right form. The right form helps them do their jobs. The pictures linked protein making, transport, and folding. Scientists usually learn more by studying these jobs together.
This matters because proteins often need the correct place and shape. If scientists study one machine alone, they can miss these links. The new method keeps the surrounding cell visible. That may reveal how cells coordinate work.
The researchers call this proof-of-concept work. They plan to apply the method to more complex cells. They will test whether other cells use similar connections.
The work is important, but it is not a finished answer. The images show frozen states, not every movement. Researchers still need to test the exact timing. They also need to study other cells. This will show which connections are widely shared.
Tiny cells showed their protein-making work
📰 Full story: A frozen 3D view shows how bacteria make, move, and shape proteins
Scientists looked inside a tiny bacterium.
Mycoplasma pneumoniae
The name of the tiny germ in the study.
protein
Small material cells use for their jobs.
cell membrane
The thin layer around a cell.
Mycoplasma pneumoniae is a tiny germ scientists studied.
Scientists froze its cells very quickly. Then they made three-dimensional pictures. Inside, one small machine made proteins. Proteins help the cell do its jobs.
The new proteins had to travel. They moved through the cell membrane. The cell membrane is a thin outside layer. Another helper system gave the proteins the right shape. The right shape helps each protein work.
The pictures showed making and moving together. Scientists did not see every moment. They saw frozen views of different moments. Next, they will study other cells.