📢 New preprint alert! How do proteins enter mitochondria? We uncovered a surprising mechanism at the mitochondrial entry gate—using #NMR, in vivo single-particle tracking, yeast experiments, and MD simulations to crack the code. www.biorxiv.org/content/10.6... #StructuralBiology #Mitochondria 🧵 1/8

We found that the cytosolic domain of Tom22— traditionally called a “receptor” — is mostly unfolded, with a short transient helix. MD simulations show the range of states. But how does a receptor interact with the incoming precursor proteins? And is this preprotein-bining even its actual role? 🧵3/8

We deciphered Tom22 ’s actual role: its transient helix competes with precursor proteins for binding to the two “real” receptor (Tom20, Tom70). In doing so, Tom22 acts as a precursor-protein displacement element, right above the TOM pore, to release precursor protein for translocation 🧵4/8

These data suggest another role: keeping Tom20 and Tom70 in vicinity of the TOM gate. We used single-molecule tracking experiments in live cells to investigate this role. Indeed: Tom22’s transient helix is a key element that keeps the receptor proteins close to the import gate. 🧵5/8

Moreover, with lots of methyl-TROSY #NMR spectra — overcoming substantial challenges related to studies of large proteins by NMR — we also resolved, for the first time, how preproteins bind Tom70. 🧵6/8

Collectively, our data reveal a new functional mechanism, which nature came up with to deal with the contradictory requirements of preprotein binding to the receptors, but also efficient release for translocation. This dynamic mechanism is likely in place at many similar systems. 🧵7/8