Like automobiles, ribosomes must pass through “quality control” after their many components are assembled. Only then can they be taken to their destination and proceed with their task – making proteins in the cell.
Quality control and ribosome export from cell nucleus to cytoplasm (schematic diagram)
Image: Ed Hurt
A team of scientists led by Prof. Dr. Ed Hurt at Heidelberg University Biochemistry Center investigated an important component in this control process. The researchers demonstrated that a specific protein, which occurs in all cells from yeast to humans, works like a molecular control switch and prevents incomplete ribosomes from leaving the “assembly hall”. The team’s findings have been published in “Nature“.
Ribosomes are macromolecular complexes consisting of a large number of parts comprising ribonucleic acids and ribosomal proteins arranged in a specific three-dimensional structure. Correct ribosome assembly is essential for the survival of all cells. The assembly process for these many components is subject to strict rules, similar to an automobile assembly line.
Before the finished car leaves the assembly hall, it is tested for full functionality and then sent to its destination. According to Prof. Hurt, there has been little research thus far on how this “quality check” takes place in ribosome assembly. The Heidelberg scientists have now identified the function of a protein from the energy-consuming GTPase family in this process.
Only correctly assembled ribosomes make it from the “assembly hall” in the cell nucleus to the cytoplasm, where they set about their real task of synthesising proteins. For export to the cytoplasm, nascent ribosomes must pass through a quality checkpoint for binding to export factor Nmd3.
Before binding, however, a signal has to be given that the assembly of the ribosome is correct and complete. Until then, a type of “control officer” occupies the site earmarked for Nmd3. The Heidelberg team has now demonstrated that this function is performed by a member of the GTPase protein family known as Nug2. Only when a specific enzyme swings into action to remodel the assembled ribosome for export to the cytoplasm, thereby consuming the energy stored by the GTPase, does the Nug2 “control officer” vacate its place and make way for export factor Nmd3. This is how the export of incomplete ribosomes is prevented.
Now that Prof. Hurt’s team has been successful in identifying the role played by control agent Nug2 in ribosome assembly, the researchers hope to gain even further insight into the functions of related proteins. These so-called nucleostemins are found in higher eukaryotes, including those of humans. The Heidelberg scientists plan to decipher the molecular mechanisms that various enzymes from the nucleostemin family use to combine the two fundamental cellular processes of ribosome formation and cell proliferation. Scientists at the University of Edinburgh (UK) also cooperated in the current research.Online information:
Marietta Fuhrmann-Koch | idw
Molecular microscopy illuminates molecular motor motion
26.07.2017 | Penn State
New virus discovered in migratory bird in Rio Grande do Sul, Brazil
26.07.2017 | Fundação de Amparo à Pesquisa do Estado de São Paulo
Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers
Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...
Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.
At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...
3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects
A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...
Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.
For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...
What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.
To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...
26.07.2017 | Event News
21.07.2017 | Event News
19.07.2017 | Event News
26.07.2017 | Physics and Astronomy
26.07.2017 | Life Sciences
26.07.2017 | Earth Sciences