Lys716 in the transmembrane domain of yeast mitofusin Fzo1 modulates anchoring and fusion.

Outer mitochondrial membrane fusion, a vital cellular process, is mediated by mitofusins. However, the underlying molecular mechanism remains elusive. We have performed extensive multiscale molecular dynamics simulations to predict a model of the transmembrane (TM) domain of the yeast mitofusin Fzo1. Coarse-grained simulations of the two TM domain helices, TM1 and TM2, reveal a stable interface, which is controlled by the charge status of residue Lys716. Atomistic replica-exchange simulations further tune our model, which is confirmed by a remarkable agreement with an independent AlphaFold2 (AF2) prediction of Fzo1 in complex with its fusion partner Ugo1. Furthermore, the presence of the TM domain destabilizes the membrane, even more if Lys716 is charged, which can be an asset for initiating fusion. The functional role of Lys716 was confirmed with yeast experiments, which show that mutating Lys716 to a hydrophobic residue prevents mitochondrial fusion. [Display omitted] • Mitofusin Fzo1 is involved in outer mitochondrial membrane fusion in yeast • Multiscale molecular dynamics predict a structure of the transmembrane domain • Lys716 controls the structure of the TM domain and destabilizes the membrane • Experiments on yeast confirm the importance of Lys716 Mitofusin Fzo1 is the protein responsible for outer mitochondrial membrane fusion in yeast. Versini et al. used multiscale molecular dynamics simulations to predict the structure of its transmembrane (TM) domain. Lys716 plays a key role in the TM domain structure and membrane destabilization. Yeast experiments confirm the importance of Lys716. [ABSTRACT FROM AUTHOR]