Fig. 3: Binding sites for dolichol lipids within ctPmt4.

A Model for the ctPmt4 TMDs viewed from the homodimer interface. Bound Dol-P and Dol-P-Man are shown in CPK representation and the TMDs are numbered. The dashed boxes correlate approximately to the detailed views shown in the other panels. B Detailed view of the active sites of ctPmt4 and scPmt1 after superimposition as in Fig. 1C. The model substrate (PYT tri-peptide) bound to scPmt2 is also superimposed and the acceptor threonine residue labelled. Conserved residues involved in substrate/product binding are labelled for ctPmt4. The distance between the bound Dol-P molecules in ctPmt4 and scPmt1 is shown by a dashed arrow and the corresponding rotation of the conserved arginine side-chain by a solid arrow. C Detailed view of the scPmt2 PYT peptide binding site superimposed with ctPmt4 as in Fig. 1C. Corresponding residues proximal to the peptide are labelled and a solid arrow shows the different conformations of the δ’ site. The attached MIR domains of scPmt1 and ctPmt4 are shown in both cartoon and surface representation. Detailed view of the ctPmt4 cytosolic binding site for the D Dol-P-Man headgroup and E dolichol tail. Residues involved in interactions with the phosphate or mannose groups or guiding the trajectory of the dolichol tail are labelled.