(A) Accessory factor density bound to the mTOR dimer. The regions of α-solenoid are indicated by surface colour, and the visible helical hairpins denoted by points (‘•’ - well-ordered regions believed to correspond to Rictor) or 5-pointed stars (‘*’ - poorly ordered regions that cannot be definitively assigned to Rictor or Protor-1). mTOR-mLST8 is shown in cartoon representation, and the mTOR active site is indicated by a large 6-pointed asterisk ‘＊’. (B) Schematic overview of the 3-dimensional layout of the mTORC2 complex in the same colour scheme. Well-ordered α-solenoidal repeat density, almost all of which will correspond to Rictor, makes up the tower and buttress. The cap and body each consist of less well-ordered density; the body comprises density connecting to the buttress, and is believed to contain both regions of Rictor and peripheral density belonging to Protor-1 (see Supplement 1), whereas the cap contains density continuing from the tower, which is believed to consist of regions of Rictor and possibly SIN1. (C) Superimposition of the mTORC2 density upon the mTORC1 model, indicating the clash between FKBP and the density corresponding to the cap (black arrow). (D) Comparison between the binding site (black arrow) of Raptor within mTORC1 (cartoon representation) and the corresponding binding site for the mTORC2 accessory factors (surface representation). All panels are coloured according to the scheme in Figure 1.