Table 2. Residues positioned at interdomain hinge points in MFS structures
MFS proteinInwardOutwardTMsPutative hinge residues
LacY1PV75GXB5–8C148, W151, A155, T265, and E269
2–11S53, S56, Q60, C355, and Q359
XylE4QIQ4GC0a5–8I172, L176, and L326
2–11L65, I69, W416, and L417
GLUT54YBQ4YBQb5–8L167, T170, V325, and T328
2–11P78, G81, and W419
YajR-3WDO5–8V142, I146, M257, and F261
2–11Q65, S344, and T345

Structures of three MFS proteins in alternate conformations were compared to identify residues involved in contacts in both states at the hinge points connecting the two six-TM domains. The proteins compared were LacY or lactose permease, the xylose transporter XylE, and the glucose transporter GLUT5 from rat (Protein Data Bank accession no. 4YBQ) and bovine (Protein Data Bank accession no. 4YB9). YajR, the template for the most recent VMAT2 models, is included for reference.

  • a For XylE, one of the conformations is occluded.

  • b Residue numbering based on Protein Data Bank accession no. 4YBQ.