Navigation Links
The molecular post office inside the cell

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.

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 th e 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.


'"/>

Source:Max-Planck-Gesellschaft


Related biology news :

1. Scientists ID molecular switch in liver that triggers harmful effects of saturated and trans fats
2. Source of molecular triggers in cutaneous T cell lymphoma identified
3. Plants, animals share molecular growth mechanisms
4. NYU researchers simulate molecular biological clock
5. Scientists reveal molecular secrets of the malaria parasite
6. Scientists identify molecular events that drive cell senescence
7. Researchers discover molecular mechanism that desensitizes us to cold
8. Findings have implications for tracking disease, drugs at the molecular level
9. Successful Test Of Single Molecule Switch Opens The Door To Biomolecular Electronics
10. At the molecular level, the predator is the prey
11. By creating molecular bridge, scientists change function of a protein
Post Your Comments:
*Name:
*Comment:
*Email:


(Date:6/9/2016)... , June 9, 2016  Perkotek an innovation leader in attendance control systems ... seamlessly log work hours, for employers to make sure the right employees are actually ... http://photos.prnewswire.com/prnh/20160609/377486LOGO ... ... ...
(Date:6/2/2016)... The Department of Transport Management (DOTM) of ... project, for the , Supply and Delivery of ... Infrastructure , to Decatur , ... Management Solutions. Numerous renowned international vendors participated in the tendering ... selected for the most compliant and innovative solution. The contract ...
(Date:5/24/2016)... -- Ampronix facilitates superior patient care by providing unparalleled technology to leaders of the ... latest premium product recently added to the range of products distributed by Ampronix. ... ... ... Display- Ampronix News ...
Breaking Biology News(10 mins):
(Date:6/24/2016)... , June 24, 2016 Epic Sciences ... detects cancers susceptible to PARP inhibitors by targeting ... cells (CTCs). The new test has already been ... in multiple cancer types. Over 230 ... damage response pathways, including PARP, ATM, ATR, DNA-PK ...
(Date:6/23/2016)... (PRWEB) , ... June 23, 2016 , ... ... is pleased to announce the launch of their brand, UP4™ Probiotics, into Target ... over 35 years, is proud to add Target to its list of well-respected ...
(Date:6/23/2016)... , June 23, 2016 Houston ... with the Cy-Fair Sports Association to serve as ... the agreement, Houston Methodist Willowbrook will provide sponsorship ... and connectivity with association coaches, volunteers, athletes and ... with the Cy-Fair Sports Association and to bring ...
(Date:6/23/2016)... , June 23, 2016   EpiBiome , a ... $1 million in debt financing from Silicon Valley Bank ... automation and to advance its drug development efforts, as ... facility. "SVB has been an incredible strategic ... services a traditional bank would provide," said Dr. ...
Breaking Biology Technology: