In Situ Structural Restraints from Crosslinking Mass Spectrometry in Human Mitochondria

The field of structural biology is increasingly focusing on studying proteins in situ, i.e. in a larger biological context. Crosslinking mass spectrometry is contributing to this effort, typically through the use of MS-cleavable crosslinkers. Here, we apply the popular non-cleavable crosslinker disuccinimidyl suberate to mitochondria and identify 5,518 distance restraints between protein residues. Each distance restraint within or between proteins provides structural information on proteins and their processes within mitochondria. Comparing these restraints to high-throughput comparative models and PDB deposited structures reveals novel protein conformations. Our data suggest substrates and flexibility of mitochondrial heat shock proteins. Crosslinking mass spectrometry is progressing towards large-scale in situ structural biology that reveals protein dynamics in addition to protein-protein interaction topologies.