Behind the picture: a tiny cell-killing drill
This image has been created by a team at the MRC Laboratory of Molecular Biology (MRC LMB) in collaboration with the University of Exeter and Birkbeck College and, for the first time, shows a detailed structure of a ‘lysenin pore’. Dr Christos Savva, an Electron Microscopy Facility scientist at the MRC LMB spoke to Sylvie Kruiniger about why understanding these structures could be the key to treating many different diseases.
It may look like some kind of technicolour mushroom but this teeny structure is actually a cell-attacking pore made of just nine proteins.
There are many different types of these pore-making proteins, each with unique receptor-binding regions that allow them to identify and bind to the surface of a specific target cell. The pore’s ‘mushroom cap’ sits on the surface of the cell and the ‘stem’ – like a needle – punctures the cell’s protective barrier, allowing its contents to seep out through the pore’s channel, causing the cell to self-destruct.
Pore-forming proteins are produced by a variety of prokaryotic and eukaryotic organisms – that includes bacteria, fungi, plants, humans and jellyfish.
This lysenin pore – or colourful mushroom – is made by earthworms to attack parasites in their gut. “The reason we studied this earthworm protein is that it is very similar to other pore-forming proteins that are harmful to humans and animals,” says Christos. “By understanding the structure of the earthworm protein we can better understand how other proteins from this family function.
“The highly specialised nature of these proteins, which only ever latch onto the surface of the specific cells they need to attack, makes them an ideal candidate for developing treatments. Like the parasites in this worm’s gut, cancer cells have a membrane that could be penetrated. Other groups are working on engineering a pore-forming protein with the right receptor-binding region to be able to latch onto a tumour, perforate its surface and make it self-destruct.
“We have been able to get such a detailed image of the structure thanks to the expertise across the groups here at the MRC Laboratory of Molecular Biology. We used cryo-electron microscopy software and detector technologies that were developed right here in the laboratory. This software and knowledge is available to the entire research community and it will help us to understand the structures of important proteins faster and accelerate the development of new treatments.”
This structure was published in Nature Communications.