We have determined the structure of the 1:1 LPHN3-OLF/FLRT3-LRR complex at 3.2 Å resolution. Overall, the complex is assembled so that the concave face of the horseshoe-shaped solenoid FLRT3-LRR interacts with LPHN3-OLF, and the central pore axis of LPHN3-OLF is oriented ~45° relatively to the FLRT3-LRR long axis (Figure 4A). The LPHN3-OLF structure in complex with FLRT3-LRR enabled us to model four more residues in a disordered loop (400-NEAT-403) and five at the C-terminal end (463-DSRGP-467) not modeled in the free protein. The FLRT3-LRR interfacing residues are mainly provided by its N-terminal moiety and are part of the capping LRRNT and the first eight LRR motifs (Figure 4B; Table S3, related to Figure 4). All three predicted N-linked glycosylation sites of FLRT3-LRR are situated far from the interface and one N-Acetyl-glucosamine moiety could be modeled on Asn226. The LPHN3-OLF residues involved in the association belong to β-strands connecting loops projected by blades I to III towards the same region of the tertiary structure next to the “entry” face (4B; Table S3, related to Figure 4). The FLRT3-LRR remaining repeats and
