TY - JOUR T1 - Disordered clusters of Bak dimers rupture mitochondria during apoptosis JF - bioRxiv DO - 10.1101/059899 SP - 059899 AU - Rachel T. Uren AU - Martin O’Hely AU - Sweta Iyer AU - Ray Bartolo AU - Jason M. Brouwer AU - Amber E. Alsop AU - Grant Dewson AU - Ruth M. Kluck Y1 - 2016/01/01 UR - http://biorxiv.org/content/early/2016/06/22/059899.abstract N2 - During apoptosis, Bak and Bax undergo major conformational change and form symmetric dimers that coalesce to perforate the mitochondrial outer membrane via an unknown mechanism. We have employed cysteine labelling and linkage analysis to the full length of Bak in mitochondria. This comprehensive survey showed that in each Bak dimer the N-termini are fully solvent-exposed and mobile, the core is highly structured, and the C-termini are flexible but restrained by their contact with the membrane. Dimer-dimer interactions were more labile than the BH3:groove interaction within dimers, suggesting there is no extensive protein interface between dimers. In addition, linkage in the mobile Bak N-terminus (V61C) specifically quantified association between dimers, allowing mathematical simulations of dimer aggregation. Together, our biochemical data and mathematical modelling show that Bak dimers form disordered, compact clusters to generate lipidic pores. These findings provide a molecular explanation for the observed structural heterogeneity of the apoptotic pore.ARTICLE HIGHLIGHTSBak dimers have very mobile, solvent-exposed N-termini, while the structured core and flexible C-termini are membrane-anchored.Interdimer interactions are weaker than the intradimer interaction.Bak dimer assembly is dynamic and lipid-mediated.Bak dimers aggregate in compact, disordered clusters to disrupt the mitochondrial outer membrane.ETOC Blurb The closely related proteins Bak and Bax are key mediators of apoptotic cell death. Here we present biochemical data and mathematical modelling that redefine how Bak dimers assemble at the molecular level to perforate the mitochondrial outer membrane. ER -