This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Scientists have often thought of cells as small, bustling cities with parts that resemble factories, power grids and shipping systems. While past research has illuminated the individual components of these cell cities, scientists haven't had the tools to probe more deeply into how those elements interact.
Researchers from Julia Mahamid's EMBL Heidelberg research group, however, have tapped the power of cryo-electron tomography (cryo-ET) to do exactly this: visualize how different cellular processes are connected. Their latest findings are published in two papers in the journal Cell. "Both projects are essentially proofs of concept for this kind of analysis," said Joe Dobbs, lead author of one of the two papers and a former Ph.D. fellow in Mahamid's group.
He is now a postdoctoral researcher at the Max Planck Institute for Brain Research in Frankfurt. "Rather than looking at a single type of molecule in isolation, both papers examine interactions between different cellular systems with a common thread of understanding how different processes are coordinated." Dobbs and colleagues focused on imaging Mycoplasma pneumoniae bacteria using cryo-ET. The imaging technique allows scientists to see inside flash-frozen cells in 3D and in great detail, revealing the structures of molecular machines.
The scientists used the technology to reconstruct high-resolution maps and count instances of the protein production machinery (ribosomes) in different functional states across hundreds of individual cells. Because proteins do much of what a cell needs to stay alive, understanding this process helps us learn how cells work, why diseases happen and how to develop better medicines. Among other findings, the scientists observed several new complexes that directly connect transcription—the process of producing mRNA from DNA—with translation, the process of producing proteins.
This helped them understand how protein production is regulated, provide structural evidence for long-hypothesized "supercomplexes" and suggest new molecular mechanisms for controlling the intertwined processes. They also found parts of the ribosome attached to the cell membrane even when they weren't producing proteins. Their results suggest that these subunits might detach from the membrane only when conditions allow a new round of protein production to begin.
This behavior is similar to what was observed in mammalian cells decades ago, and the new findings suggest that such mechanisms may be conserved from bacteria to humans. "I think of it as a city," Dobbs said. "The molecular machines I work on are like little factories that produce things, while some of my colleagues have been studying systems that transport and process those products.
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