M. Handford, C. Rodriguez-Furlán and A. Orellana. Nucleotide-sugar transporters: structure, function and roles in vivo. Braz J Med Biol Res 2006; 39: 1149-1158.  

Figure 4. Conserved residues in nucleotide-sugar transporters from group 2. The conserved residues K and T present in the NSTs that belong to group 2 are boxed in black. It can be observed that these residues are part of putative transmembrane domains (TMD) except for the human GDP-fucose transporter.