Molecular biology mystery unravelled

The nature of the machinery responsible for the entry of proteins into cell membranes has been unravelled by scientists, who hope the breakthrough could ultimately be exploited for the design of new anti-bacterial drugs.

Groups of researchers from the University of Bristol and the European Molecular Biology Laboratory (EMBL) used new genetic engineering technologies to reconstruct and isolate the cell’s protein trafficking machinery. Its analysis has shed new light on a process which had previously been a mystery for molecular biologists.

The findings, published this week in the Proceedings of the National Academy of Sciences (PNAS), could also have applications for synthetic biology - an emerging field of science and technology, for the development of novel membrane proteins with useful activities.

Proteins are the building blocks of all life and are essential for the growth of cells and tissue repair. The proteins in the membrane typically help the cell interact with its environment and conserve energy. 

Researchers were able to identify the ‘holo-translocon’ as the machinery which inserts proteins into the membrane. It is a large membrane protein complex and is uniquely capable of both protein-secretion and membrane-insertion.

Professor Ian Collinson, from the School of Biochemistry at Bristol University, 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. Having unravelled how this vital holo-translocon works, we’re now in a position to look at its components to see if they can help in the design or screening for new anti-bacterial drugs.”

Separation of a cell

This illustration shows a cell undergoing mitosis or “cell division.” The cell membrane is shown in blue, and the cell’s chromosomes are shown in yellow. Mitosis is a well-studied and well-imaged phenomenon in two-dimensional images, but it’s never before been seen quite like this. What makes this image special is the use of a new fluorescent protein called MiniSOG, shown flying out of the cell.

Image courtesy of Andrew Noske and Thomas Deerinck (National Center for Microscopy and Imaging Research, University of California, San Diego); Horng Ou and Clodagh O’Shea (Salk Institute).

(Source: MSNBC)

Artificial Beginnings: Understanding the Origin of Life by Recreating It

The Origin of Life on Earth was certainly, in retrospect, and from the human vantage point, the most fateful event in the history of the Universe. On a young, tepid Earth chemistry sprung into biology and set course on a four billion year journey that would eventually lead to us. However, all traces of the first, primitive organisms have vanished. They were outcompeted and devoured by their evolutionary descendents, leaving nothing to form fossils. Though we will never be able to set eyes on the first Earthlings, the first pioneers, we can understand what they must have been like through more subtle, indirect approaches. Comparative biochemistry across the whole of life takes us back quite a ways, though not to the first cells. The most recent common ancestor shared by all living organisms—bacteria, plants, animals, fungi, archaea, and unicellular eukaryotes like amoebae—was born long after the first cell ceased to exist. The only way we can truly understand what life must have been like in its earliest days is to create it ourselves.

To investigate membrane fusion during synaptic transmission (top), Rothman, Pincet, and colleagues designed an artificial version of the event. They exposed lipid nanodiscs embedded with SNARE proteins to vesicles containing complementary SNARE proteins. Only one SNARE protein complex was required for fusion between the discs and vesicles (A), but three were necessary to create a stable pore to release the neurotransmitter contained within the vesicle (B).

SNAREs at the Synapse