Many newly synthesized proteins will pass their lives within the confines of the cell, but many others end up secreted or embedded in the cellular membrane.
Such proteins are labeled by specific ‘tags’ encoded in their sequences, which get recognized by proteins that escort them to the pore-like translocon protein complex. In bacteria, translocons are situated in the inner cell membrane. They remain effectively closed until they interact with an escorted protein, at which point the pore opens and allows the protein to pass through the membrane.
The central pore complex of the bacterial translocon is formed by a trio of proteins: SecY, SecE and SecG. Pore opening is initiated via interaction of the SecYEG complex with an additional protein, SecA, although many mechanistic details of this process remain unclear.
Now, new work from a multi-institutional research team, led by Osamu Nureki of the University of Tokyo and Koreaki Ito of Kyoto University, and including RIKEN scientists Naoshi Dohmae and Yuji Sugita of the Advanced Science Institute in Wako, has yielded valuable new insights into this process (1).
The team generated crystals of the SecYE complex from the bacterium Thermus thermophilus, assisted by the inclusion of an antibody fragment that helped to stabilize the complex, and then compared this structure against a previously determined structure of the ‘closed’ translocon from a primitive bacterial species that lacks SecA2. This comparison revealed the existence of an opening absent from the closed structure, suggesting that the SecYE-antibody complex had assumed a transitional ‘pre-open’ state.
Follow-up analysis yielded multiple lines of evidence that the antibody interaction with SecYE mirrors the association of this complex with SecA, suggesting that the structure seen here is a true intermediate in the translocon opening process, and that SecA binding induces formation of an entry point in SecYE for translocation-ready proteins. This transition of SecYE into the pre-open state also appears to induce major conformational changes in SecA, which enable it to act as a motor for facilitating protein transit through the translocon pore.
Dohmae and Sugita are continuing to collaborate in the further examination of this mechanism, using chemical analysis techniques and computational simulations to confirm that the model developed based on these findings reflects the reality of how these proteins interact in the cell, but both researchers are pleased with these initial structural insights. “This crystal structure is useful to understand the early process of polypeptide translocation through Sec channels,” says Sugita.
1. Tsukazaki, T., Mori, H., Fukai, S., Ishitani, R., Mori, T., Dohmae, N., Perederina, A., Sugita, Y., Vassylyev, D.G., Ito, K. & Nureki, O. Conformational transition of Sec machinery inferred from bacterial SecYE structures. Nature 455, 988–991 (2008).
2. Van den Berg, B., Clemons, W.M., Collinson, I., Modis, Y., Hartmann, E., Harrison, S.C. & Rapoport, T.A. X-ray structure of a protein-conducting channel. Nature 427, 36–44 (2004).
The corresponding author for this highlight is based at the RIKEN Biomolecular Characterization Team
‘Farming’ bacteria to boost growth in the oceans
24.10.2016 | Max-Planck-Institut für marine Mikrobiologie
Calcium Induces Chronic Lung Infections
24.10.2016 | Universität Basel
Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion
Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
24.10.2016 | Earth Sciences
24.10.2016 | Life Sciences
24.10.2016 | Physics and Astronomy