Navigation Links
Protein structure: Peering into the transit pore
Date:2/7/2014

The lipid-rich membranes of cells are largely impermeable to proteins, but evolution has provided a way through in the form of transmembrane tunnels. A new study shows in unmatched detail what happens as proteins pass through such a pore.

Every cell is surrounded by a surface membrane and contains internal compartments bounded by membranes. Almost one-third of all proteins synthesized in cells must pass through these membranes or be incorporated into them in order to fulfil their functions. However, the fat-rich nature of membranes makes it impossible for most proteins to percolate through them directly. Therefore, biological membranes contain so-called protein-conducting channels, molecular pores through which proteins can pass. "Structural investigations have already provided clues to how proteins are inserted into the membrane and then drawn through it like a length of thread to emerge on the other side," says Professor Roland Beckmann of the Gene Center of Ludwig-Maximilians-Universitaet (LMU) in Munich. "However, conclusive proof for these mechanisms has been lacking until now."

Protein-conducting channels are known to be shaped like an hour-glass, consisting of two cones connected by a narrow central constriction. In the inactive form, the constriction is blocked by a plug that protrudes from the side-wall. Presumably, if a protein is to cross the membrane, the channel must be opened to provide a continuous aqueous environment for its passage. If, on the other hand, a protein is to be inserted within the membrane itself, it must emerge from a lateral opening within the tunnel.

Imaging the crucial transition

"Up until now, it had not been possible to characterize these structural transitions with the required spatial and temporal resolution," Beckmann says. Now he and his colleagues have, for the first time, succeeded in isolating transitional forms of the active channel, and elucidating their three-dimensional structures with the help of cryo-electron microscopy at the unprecedented resolution of less than 1 nanometer. "This allowed us to determine the spatial conformations of the individual protein strands that make up the channel and to analyze how the channel behaves during its functional cycle," he explains.

Indeed, the researchers were even able to capture a snapshot of the complex at the moment when a protein leaves the channel to be incorporated into the cell membrane. "It turns out that there actually is a side-door within the channel, which opens to allow the protein to diffuse into the membrane," Beckmann says. Interestingly, as the lateral gate opens and the protein exits the channel into the membrane, the plug moves into the central constriction, blocking access to the outside and preventing diffusion of ions through the now empty channel. Surprisingly, proteins destined to cross the membrane do so without altering the position of the plug very much. Instead, an adjacent strand shifts slightly outward, widening the constriction sufficiently to let the protein through the length of the tunnel.

Beckmann and his team now hope to be able to increase the resolution of their snapshots still further. "Our goal is to achieve a resolution of less than 0.4 nm, in order to discern the interactions in molecular detail and understand the dynamic changes that take place in the structure of the channel," he says. In addition, the scientists want to image other membrane protein complexes such as visual pigments and analyze how a single chain of amino acids can function as a dynamically active membrane receptor.


'/>"/>

Contact: Luise Dirscherl
dirscherl@lmu.de
49-892-180-2706
Ludwig-Maximilians-Universitt Mnchen
Source:Eurekalert

Related biology news :

1. Protein synthesis and chance
2. Designer proteins provide new information about the bodys signal processes
3. The Protein Society announces the selection of 2 Protein Science Best Paper speakers
4. Researchers tune in to protein pairs
5. FASEB announces 2014 Science Research Conference: Protein Folding in the Cell
6. FASEB announces 2014 SRC: Protein Phosphorylation, Cellular Plasticity & Signaling Rewiring
7. FASEB announces 2014 SRC: Protein Interactions, Structures, Technologies & Networks
8. High-protein diets, like the Dukan diet, increase the risk of developing kidney disease
9. Overexpression of splicing protein in skin repair causes early changes seen in skin cancer
10. Next-gen reappraisal of interactions within a cancer-associated protein complex
11. Researchers pursuing arthritis protein
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/19/2016)... , UAE, April 20, 2016 ... be implemented as a compact web-based "all-in-one" system solution ... the biometric fingerprint reader or the door interface with ... of modern access control systems. The minimal dimensions of ... ID readers into the building installations offer considerable freedom ...
(Date:4/15/2016)... 2016 Research and Markets has ... Market 2016-2020,"  report to their offering.  , ... ,The global gait biometrics market is expected to ... period 2016-2020. Gait analysis generates multiple ... used to compute factors that are not or ...
(Date:4/13/2016)... -- IMPOWER physicians supporting Medicaid patients in Central ... in telehealth thanks to a new partnership with higi. ... patients can routinely track key health measurements, such as ... when they opt in, share them with IMPOWER clinicians ... retail location at no cost. By leveraging this data, ...
Breaking Biology News(10 mins):
(Date:4/28/2016)... Hill, Conn. (PRWEB) , ... April 28, 2016 ... ... of financing and ongoing support for Connecticut's innovative, growing companies, today announced the ... digital health and financial technology (fintech) companies. , “VentureClash looks to ...
(Date:4/27/2016)... ... , ... Shimadzu Scientific Instruments (SSI) will be showcasing a ... and Expo. Shimadzu’s high-performance instruments enable laboratories to test cannabis products for potency, ... by booth 1021 to learn how Shimadzu’s instruments can help improve QA/QC testing, ...
(Date:4/27/2016)... ... April 27, 2016 , ... The Board of Directors of ... John Tilton as Chief Commercial Officer.  Mr. Tilton joined Biohaven from Alexion Pharmaceuticals, ... leaders responsible for the commercialization of multiple orphan drug indications. Mr. Tilton ...
(Date:4/27/2016)... ... ... Global Stem Cells Group and the University of Santiago Biotechnology ... development initiatives for potential stem cell protocol management for 2016 – 2020. , ... meeting to establish a working agenda and foster initiatives to promote stem cell research ...
Breaking Biology Technology: