Huizing et al. Page 26 A uthor Man uscr ipt A uthor Man Figure 3: Topology model of SLC17A5 Simplified model of SLC17A5 (not to scale). SLC17A5 consists of 495 amino acids, 12 transmembrane domains and a N-terminal dileucine sorting motif (DRTPLL). Three frequent FSASD mutations are indicated (*). Transmembrane domain 4 (striped) lines a uscr large aqueous cavity that is part of the substrate permeation pathway [4, 5]. ipt A uthor Man uscr ipt A uthor Man uscr ipt Neurosci Lett. Author manuscript; available in PMC 2021 June 11.