Table 2. Residues positioned at interdomain hinge points in MFS structures.

MFS protein	Inward	Outward	TMs	Putative hinge residues
LacY	1PV7	5GXB	5–8	C148, W151, A155, T265, and E269
			2–11	S53, S56, Q60, C355, and Q359
XylE	4QIQ	4GC0a	5–8	I172, L176, and L326
			2–11	L65, I69, W416, and L417
GLUT5	4YBQ	4YBQb	5–8	L167, T170, V325, and T328
			2–11	P78, G81, and W419
YajR	-	3WDO	5–8	V142, I146, M257, and F261
			2–11	Q65, 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.

^aFor XylE, one of the conformations is occluded.

^bResidue numbering based on Protein Data Bank accession no. 4YBQ.