Proteins are impressive molecular buildings both in size and function. These building blocks of life are composed of hundreds, sometimes thousands of amino acids that self-assemble to form complex biological machines, responsible for essential cell functions. Most of the time, biologists need to divide them into smaller, more stable blocks to study them using conventional biochemical and biophysical techniques. Yet such manipulations create a gap from reality, as self-assembly is a process that includes fleeting intermediate states.
With their Mexican collaborators from Morelos University, researchers from IBS were able to create the first "film" of this self-assembly process in the case of a large biological machinery. They developed innovative approaches for the real-time observation, without introducing any artificial perturbation, of the molecular arrangements in an enzyme called aminopeptidase. This protein has a molecular weight of half a megadalton, which equals to about 5,000 amino acids. Through an integrated approach combining Nuclear Magnetic Resonance (NMR), electron microscopy and mass spectrometry native1, the scientists were able to structurally monitor the self-assembly of twelve sub-units forming this aminopeptidase. This process is essential for the reprocessing of proteins in bacteria and archea. For this purpose, they developed isotopic labeling strategies that make it possible to study objects weighing a few hundreds of kilodaltons. These technologies have led to three patents (co-property of CEA/CNRS/UGA) with industrial applications marketed by start-up NMR-Bio founded by the researchers from Grenoble.