Scientists map one of life's molecular mysteries

Jan 26, 2012

All living organisms are made up of cells, behind these intricate life forms lie complex cellular processes that allow our bodies to function. Researchers working on protein secretion — a fundamental process in biology — have revealed how protein channels in the membrane are activated by special signals contained in proteins destined for secretion. The results help explain the underlying mechanism responsible for the release of proteins such as hormones and antibodies into the blood stream.

The findings, published today in the inaugural issue of Cell Reports, represent a major step forward in cell biology. Until now, scientists have been frustrated by not knowing the architecture of the protein transport machinery when engaged by cargo. However, the team led by researchers from the University of Bristol as part of an international collaboration, has successfully produced and visualised such a complex.

All cells are surrounded by membranes, made up from a double layer of fatty molecules called phospholipids. These act as an ideal 'skin', keeping the cell's insides in. In the absence of other components these fatty molecules act as barriers, preventing the necessary rapid exchange of nutrients and waste products, and of larger molecules like proteins, between the environment and the cell interior. However, such movement is required for many proteins to perform their biological functions either within the membrane or the outside.

To overcome this problem, biological membranes contain a number of translocation systems that enable proteins and other useful substances to pass across the phospholipid barrier. In the case of proteins, those destined for transport are recognised by translocation systems via signals embedded in the sequence of amino acids from which they are constructed. Correct passage through or across the membrane is critical in ensuring that complete their lifecycle and fulfill their function.

Using electron microscopy and results from X-ray crystallography, Ian Collinson, Professor of Biochemistry at the University, and his team have described the structure of the ubiquitous Sec-complex associated with a bona fide mimic of a pre-secretory in the native environment of the membrane. These results reveal how the binding of the signal sequence unlocks the Sec-complex prior to channel opening and pre-protein transport.

Professor Collinson from the University's School of Biochemistry, said: "These findings are important as they address outstanding questions in one of the central pillars of biology, a process essential in every cell in every organism. The results may suggest ways in which the process can be corrupted in order to manage specific disease states or bacteria infections."

Explore further: Surprise: Lost stem cells naturally replaced by non-stem cells, fly research suggests

More information: The paper, entitled Structure of the SecY complex unlocked by a pre-protein mimic, by Hizlan, D, Robson, A, Whitehouse, S, Gold, V.A, Vonck, J, Mills, D.J, Kühlbrandt, W. and Collinson, I. is published in Cell Reports.

Related Stories

Proteins find their way with address label and guide

Feb 23, 2011

Most newly produced proteins in a cell need to be transported to the proper place before they can be put to work. For proteins to find their way, they have a built-in signal linked to them, a kind of address ...

Biologists search for 'half-fusion'

May 16, 2005

Every living cell is surrounded by a membrane, a thin barrier that separates the genetic machinery of life from the non-living world outside. Though barriers, membranes are not impervious. Cells use a complex hierarchy of ...

Putting light-harvesters on the spot

Oct 19, 2011

How the light-harvesting complexes required for photosynthesis get to their site of action in the plant cell is reported by RUB biologists in the Journal of Biological Chemistry. The team led by Prof. Dr. Danja Schunemann has de ...

Recommended for you

For resetting circadian rhythms, neural cooperation is key

11 hours ago

Fruit flies are pretty predictable when it comes to scheduling their days, with peaks of activity at dawn and dusk and rest times in between. Now, researchers reporting in the Cell Press journal Cell Reports on April 17th h ...

Rapid and accurate mRNA detection in plant tissues

12 hours ago

Gene expression is the process whereby the genetic information of DNA is used to manufacture functional products, such as proteins, which have numerous different functions in living organisms. Messenger RNA (mRNA) serves ...

For cells, internal stress leads to unique shapes

Apr 16, 2014

From far away, the top of a leaf looks like one seamless surface; however, up close, that smooth exterior is actually made up of a patchwork of cells in a variety of shapes and sizes. Interested in how these ...

User comments : 0

More news stories

Deadly human pathogen Cryptococcus fully sequenced

Within each strand of DNA lies the blueprint for building an organism, along with the keys to its evolution and survival. These genetic instructions can give valuable insight into why pathogens like Cryptococcus ne ...

Hackathon team's GoogolPlex gives Siri extra powers

( —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...