Today scientists at the Institute for Research in Biomedicine (IRB Barcelona) at the Barcelona Science Park present a study in Cell where they have been able to observe protein nanomachines (also called protein complexes)—the structures responsible for performing cell functions—for the first time in living cells and in 3D. This work has been done in collaboration with researchers at the University of Geneva in Switzerland and the Centro Andaluz de Biología del Desarrollo in Seville.

Currently, biologists who study the function of protein nanomachines isolate these complexes in test tubes, divorced from the cell, and then apply in vitro techniques that allow them to observe their structure up to the atomic level. Alternatively, they use techniques that allow the analysis of these complexes within the living cell but that give little structural information. In this study, the scientists have managed to directly observe the structure of the protein machinery in living cells while it is executing its function.

“The in vitro techniques available are excellent and allow us to make observations at the atomic level, but the information provided is limited. We will not know how an engine works if we dissemble it and only look at the individual parts. We need to see the engine assembled in the car and running. In biology, we still do not have the tools to observe the inner workings of a living cell, but the technique that we have developed is a step in the right direction and we can now see, in 3D, how the protein complexes carry out their functions,” explains Oriol Gallego, IRB Barcelona researcher and coordinator of the group that undertook this study, which also involved PhD student Irene Pazos.
 

Watching the nanometric machinery at work

The new strategy brings together methods from super-resolution microscopy—a discovery that was recognised with the 2014 Nobel Prize in Chemistry—, cell engineering, and computational modelling. The technology allows us to observe protein complexes with a precision of 5 nm*, a resolution “four times better than that offered by super-resolution and that allows us to perform cell biology studies that were previously unfeasible,” explains Gallego. (*a nm is a millionth part of a mm. A hair has a width of 100,000 nm)

The researchers genetically modify cells in order to build artificial supports inside onto which they can anchor protein complexes. These supports are designed in such a way as to allow them to regulate the angle from which the immobilized nanomachinery is viewed. After, in order to determine the 3D structure of the protein complex, they use super-resolution techniques to measure the distances between different components and then integrate them in a process similar to that used by GPS.
 

•More information on IRB website [+]