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: Fighting bacteria—with viruses

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

Fighting bacteria—with viruses

Jul 24, 2014

Research published today in PLOS Pathogens reveals how viruses called bacteriophages destroy the bacterium Clostridium difficile (C. diff), which is becoming a serious problem in hospitals and healthcare institutes, due to its re ...

Atomic structure of key muscle component revealed

Jul 24, 2014

Actin is the most abundant protein in the body, and when you look more closely at its fundamental role in life, it's easy to see why. It is the basis of most movement in the body, and all cells and components ...

Brand new technology detects probiotic organisms in food

Jul 23, 2014

In the food industr, ity is very important to ensure the quality and safety of products consumed by the population to improve their properties and reduce foodborne illness. Therefore, a team of Mexican researchers ...

Protein evolution follows a modular principle

Jul 23, 2014

Proteins impart shape and stability to cells, drive metabolic processes and transmit signals. To perform these manifold tasks, they fold into complex three-dimensional shapes. Scientists at the Max Planck ...

Report on viruses looks beyond disease

Jul 22, 2014

In contrast to their negative reputation as disease causing agents, some viruses can perform crucial biological and evolutionary functions that help to shape the world we live in today, according to a new report by the American ...

User comments : 0