The Golgi apparatus serves as a cellular post office, sending the cell’s many proteins to their correct destinations. In order to mark and sort the proteins, the Golgi has an elaborate architecture.
It consists of flat membrane-enclosed compartments (called cisternae) that are densely packed on top of each other, like a stack of pancakes. Researchers at the Max Planck Institute of Biochemistry in Martinsried, Germany, have now identified structures within these cisternae.
“Using cryo-electron tomography, we discovered that the cisterna membranes are held together by linker proteins,” explains Benjamin Engel, first author of the study. Their results have been published in the journal PNAS.
After being produced at the endoplasmic reticulum, proteins enter the Golgi apparatus and travel through its stacks of cisterna membranes. As the proteins move through the cisternae, they receive a variety of modifications and are finally sorted into vesicles for delivery to different locations inside and outside the cell.
The elaborate membrane architecture of the Golgi is crucial for regulating the modification and sorting of cargo proteins, as different Golgi enzymes are localized to specific cisterna stacks. However, many questions remain about how the Golgi architecture is established. Researchers at the MPI of Biochemistry helped answer these questions by using in situ cryo-electron tomography to identify new molecular structures inside the Golgi of the alga Chlamydomonas.
Until recently, researchers could only use traditional electron microscopy to look closely at cellular structures. However, the sample preparation steps required for this technique can damage the specimen and thus prevent the observation of fine molecular details.
Scientists in the “Molecular Structural Biology“ Department, led by Prof. Wolfgang Baumeister, have engineered a method called in situ cryo-electron tomography. The cell is rapidly frozen to preserve its delicate structure and then thinned with a focused ion beam, revealing the cellular interior. Next, an electron microscope is used to acquire a three-dimensional view of the unperturbed molecular environment inside the cell.
Experts in the Golgi field assumed for a long time that the cisterna stacks were not held together by linker proteins. By using cryo-electron tomography to look at the Golgi apparatus, Benjamin Engel and his colleagues discovered arrays of proteins between the cisterna membranes (see figure), which had gone unseen using other techniques. “The way the protein arrays hold two Golgi membranes together is similar to how a zipper works when you put on a jacket”, explains PhD student Shoh Asano, co-author of the study.
The researchers believe that the protein arrays may have several functions to help the Golgi carry out its role as the cell’s post office. Do these structures define a sub-compartment of the Golgi that accelerates the enzyme reactions used to modify cargo proteins? Do the protein arrays physically force larger cargo proteins to the periphery of the Golgi, where they are sorted into vesicles for delivery? These are questions that Benjamin Engel and his colleagues want to solve in the future.
B. D. Engel, M. Schaffer, S. Albert, S. Asano, J. M. Plitzko and W. Baumeister: In situ structural analysis of Golgi intracisternal protein arrays. Proceedings of the National Academy of Sciences USA, September 8, 2015
Prof. Dr. Wolfgang Baumeister
Molecular Structural Biology
Max Planck Institute of Biochemistry
Am Klopferspitz 18
Max Planck Institute of Biochemistry
Am Klopferspitz 18
Tel. +49 89 8578-2824
http://www.biochem.mpg.de/en/news - More press releases of the MPI of Biochemistry
http://www.biochem.mpg.de/baumeister - Website of the Research Department "Molecular Structural Biology" (Wolfgang Baumeister)
Anja Konschak | Max-Planck-Institut für Biochemie
Immune Defense Without Collateral Damage
23.01.2017 | Universität Basel
The interactome of infected neural cells reveals new therapeutic targets for Zika
23.01.2017 | D'Or Institute for Research and Education
For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.
According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
23.01.2017 | Health and Medicine
23.01.2017 | Physics and Astronomy
23.01.2017 | Process Engineering