In order to generate as many proteins as possible at the same time, several ribosomes cluster together to form an "industrial complex" - the polysome - and read simultaneously the same messenger molecule. Scientists at the Max-Planck-Institute of Biochemistry have now, for the first time, been able to reveal the three-dimensional structure of these complexes (Cell 23.1.2009).
Figure: The three dimensional strucuture of the polysome:Cryoelectron tomographic picture of two polysomes (left), schematic diagram of their structure (middle) and the messenger molecule (mRNA) pathway within the polysome (right). The small ribosomal subunits (yellow) are oriented towards the inside of the polysome, the large subunits (blue) and the nascent protein chains (indicated by red cones) face the cytosol. If the ribosomes are continuously arranged in a \"top-to-top\" orientation (Fig. A, middle), the result is a pseudo-helical structure of the polysome. If the ribosomes are arranged alternating in \"top-to-top\" and in \"top-to-bottom\" orientation (Fig. B, middle), the result is a staggered structure. In both cases the mRNA traverses the shortest possible path from one ribosome to its next neighbor (Fig A and B, right). Florian Brandt, Max-Planck-Institut für Biochemie
In a polysome, the ribosomes are densely packed and exhibit preferred orientations: The small ribosomal subunits are orientated towards the inside of the polysome and the ribosomes are arranged either in a staggered or in a pseudo-helical structure (see figure). This arrangement ensures that the distance between nascent protein chains is maximized, thereby reducing the probability of intermolecular interactions that would give rise to aggregation and limit productive folding. Until now, the belief has been that specialised proteins, the so-called chaperones, would prevent protein misfolding.
Against the background of the new findings, their function appears in a new light: "It appears possible that the main function of chaperones that interact with nascent polypeptide chains is not to suppress chain aggregation within polysomes, but rather to reduce intra-chain misfolding as well as aggregation between different polysomes in the crowded cellular environment", explains Ulrich Hartl, head of the "Cellular Biochemistry" department, who lead the project in cooperation with Wolfgang Baumeister, head of the "Molecular Structural Biology" department.
Moreover, the spatial structure of the polysome enables the ribosomes to process the messenger molecule in the protected area within the polysome and to pass it on without detours. Thus, the architecture of the cellular protein factories facilitates an optimized work flow and increases the efficiency of protein folding.
Original Publication:The Native 3D Organization of Bacterial Polysomes; Florian Brandt, Adrian H. Elcock, Stephanie A. Etchells, Julio O. Ortiz, F. Ulrich Hartl and Wolfgang Baumeister;
Cell, DOI 10.1016/j.cell.2008.11.016
Single-stranded DNA and RNA origami go live
15.12.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard
New antbird species discovered in Peru by LSU ornithologists
15.12.2017 | Louisiana State University
DNA molecules that follow specific instructions could offer more precise molecular control of synthetic chemical systems, a discovery that opens the door for engineers to create molecular machines with new and complex behaviors.
Researchers have created chemical amplifiers and a chemical oscillator using a systematic method that has the potential to embed sophisticated circuit...
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
15.12.2017 | Power and Electrical Engineering
15.12.2017 | Materials Sciences
15.12.2017 | Life Sciences