Protein structures in the context of time and space by mass spectrometry.

Insights of tremendous value can and have been obtained using current structural elucidation methods. Possibly the largest caveat of these methods is that proteins are typically investigated as static molecules and outside their native environments. Many proteins and especially multi-protein complexes do not behave under such conditions and their structure cannot or only in parts be determined. Even these structures are possibly compromised, though, as isolating a protein from its native environ ment removes interaction partners that might impact on structure and function of the protein. Here we are developing an approach that analyses the structure and dynamics of proteins within their native contexts. We use cross-linking/mass spectrometry (CLMS), an approach we helped to pioneer during my previous Fellowship. CLMS excels already as a part of integrated structural biology. In addition, we propose that CLMS can generate structural insights on many currently difficult targets especi ally by focussing on them in their native environments. Furthermore, quantitative and time-resolved CLMS will reveal protein dynamics and transient structures. We use new chemistry to elucidate protein structures at surprisingly high definition. We will investigate MeCP2, a protein with important biological functions in the context of chromatin, but whose structure cannot be determined in isolation. We will also define an unprecedented view of the various activated conformations of C1, a key protein of the innate immune system. Through these advances, we envision mass spectrometry will become a key tool used to unravel protein structure, contacts, conformational changes and transient structures in native supramolecular environments.