Featured Research

from universities, journals, and other organizations

The Molecular Post Office Inside the Cell

Date:
May 15, 2006
Source:
Max-Planck-Gesellschaft
Summary:
For most proteins, there is a particular place inside a cell where they carry out their function. But how do they get there? Scientists from the Charité Berlin, the University of Heidelberg, and the Max Planck Institute for Molecular Genetics in Berlin have now been able to visualize the structure of a "molecular machine" involved in protein sorting using cryo-electron microscopy and single particle analysis.

Rearrangement of SRP bound to the ribosome exposes the translocon binding sites on the ribosome surface.
Credit: Image : Max Planck Institute for Molecular Genetics

For most proteins, there is a particular place inside a cell where they carry out their function. But how do they get there? Scientists from the Charit Berlin, the University of Heidelberg, and the Max Planck Institute for Molecular Genetics in Berlin have now been able to visualize the structure of a "molecular machine" involved in protein sorting using cryo-electron microscopy and single particle analysis.

Related Articles


This "machine" is made up of a single active ribosome, plus a special signal recognition protein and a matching receptor. The scientists have shown that when the three proteins interact, certain areas open up on the ribosome, which allows the ribosome to dock onto another complex. The later complex, which is called translocon complex, takes over the job of transferring a newly produced protein through the membrane. Knowing the structure of the molecular machine helps scientists to understand how secretory and membrane proteins in a cell are expressed and sorted (Science, May 5, 2006).

Sorting proteins is fundamental to the gene expression of every organism - from bacteria to humans. Particularly important during biosynthesis is sorting secretory and membrane proteins, which have to find the way to their final destination inside or outside the cell. Secretory proteins are those that later on leave the cell, like anti-bodies. Membrane proteins are proteins embedded into the cell’s membranes - for example, signalling receptors. One particular molecular complex is important in protein sorting. It is made from an active ribosome - that is, the protein synthesis machine in the cell - called the signal recognition particle (SRP), and its corresponding receptor. It is the structure of this complex that the scientific team is now able to describe.

The key element to this machine's functioning is a signal sequence located at the N-terminal end of the protein to be sorted. The sequence acts as a kind of "postal code" in the cell. The SRP reads the sequence as soon as the newly built protein chain leaves the ribosome. The SRP binds to the ribosome and directs it, together with the SRP receptor, to what is called the "translocon complex" in the membrane of the endoplasmic reticulum. The translocon complex is made of a "protein conducting channel" and other membrane proteins. The ribosome is anchored at the translocon and continues with protein biosynthesis.

Notable is that the ribosome can no longer bind to the translocon as soon as the SRP has bound to the ribosome. The ribosome needs additional support from the SRP receptor, which it transfers from the SRP to the translocon. Now that scientists understand the structure of the complex, they can see how the receptor interacts with ribosome and SRP and replaces parts of the SRP molecule. In this way, specific sites are made available for the translocon, which allows it to bind to the ribosome. Understanding this key event during protein sorting is essential to understanding how secretory and membrane proteins are expressed in a cell.

The Berlin UltraStruckturNetzwerk (USN)

The UltraStrukturNetzwerk (translated, "ultra structure network") is a research network aimed at understand complicated "molecular machines" using the most modern of methods, including mass spectrometry and cryo- microscopy.

The USN, initiated by the Max Planck Institute for Molecular Genetics in co-operation with Charit; brings together more than 15 research groups in the Berlin-Brandenburg region. These groups come from the three Berlin Universities (Free, Technical, and Humboldt), the Max Delbrck Center for Molecular Medicine, the Leibniz Institute of Molecular Pharmacology, the University of Potsdam and the Max Planck Institute of Molecular Plant Physiology in Potsdam.

The USN has established the technological infrastructure to analyse molecular machines through the support of the European Union and the Senatsverwaltung fr Wissenschaft, Forschung und Kultur Berlin, with a total contribution of 8 million euros. Core facilities are located at the Max Planck Institute for Molecular Genetics; they include a 300 kV Tecnai G2 Polara cyro microscope. The research presented in this article contains some of the first results from the network.


Story Source:

The above story is based on materials provided by Max-Planck-Gesellschaft. Note: Materials may be edited for content and length.


Cite This Page:

Max-Planck-Gesellschaft. "The Molecular Post Office Inside the Cell." ScienceDaily. ScienceDaily, 15 May 2006. <www.sciencedaily.com/releases/2006/05/060515000652.htm>.
Max-Planck-Gesellschaft. (2006, May 15). The Molecular Post Office Inside the Cell. ScienceDaily. Retrieved November 22, 2014 from www.sciencedaily.com/releases/2006/05/060515000652.htm
Max-Planck-Gesellschaft. "The Molecular Post Office Inside the Cell." ScienceDaily. www.sciencedaily.com/releases/2006/05/060515000652.htm (accessed November 22, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Saturday, November 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Could Your Genes Be The Reason You're Single?

Could Your Genes Be The Reason You're Single?

Newsy (Nov. 21, 2014) Researchers in Beijing discovered a gene called 5-HTA1, and carriers are reportedly 20 percent more likely to be single. Video provided by Newsy
Powered by NewsLook.com
Raw: Baby Okapi Born at Houston Zoo

Raw: Baby Okapi Born at Houston Zoo

AP (Nov. 20, 2014) The Houston Zoo released video of a male baby okapi. Okapis, also known as the "forest giraffe", are native to the Democratic Republic of the Congo in Central Africa. Video is mute from source. (Nov. 20) Video provided by AP
Powered by NewsLook.com
Your Complicated Job Might Keep Your Brain Young

Your Complicated Job Might Keep Your Brain Young

Newsy (Nov. 20, 2014) Researchers at the University of Edinburgh found the more complex your job is, the sharper your cognitive skills will likely be as you age. Video provided by Newsy
Powered by NewsLook.com
Mysterious Glow Worms Found in the Amazon

Mysterious Glow Worms Found in the Amazon

Buzz60 (Nov. 20, 2014) Wildlife photographer Jeff Cremer teamed up with entomologist Aaron Pomerantz and others to investigate a predatory glow worm found in the Amazon. Patrick Jones (@Patrick_E_Jones) explains. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins