Six-transmembrane helical domain 1 (TMD1) of the ABC transporters, subfamily C
This group represents the six-transmembrane domain 1 (TMD1)of the ABC transporters that belong to the ABCC subfamily, such as the sulphonylurea receptors SUR1/2 (ABCC8), the cystic fibrosis transmembrane conductance regulator (CFTR, ABCC7), Multidrug-Resistance associated Proteins (MRP1-9), VMR1 (vacuolar multidrug resistance protein 1), and YOR1 (yeast oligomycin resistance transporter protein). This TM subunit exhibits the type 3 ATP-binding cassette (ABC) exporter fold, which is characterized by 6 TM helices per subunit (domain), or a total of 12 TM helices for the complete transporter. The type 3 ABC exporters are found in both prokaryotes and eukaryotes, where they mediate the cellular secretion of toxic compounds, a various type of lipids and polypeptides. ABC transporters typically consist of two transmembrane domains (TMDs) and two nucleotide-binding domains (NBDs). The two NBDs together bind and hydrolyze ATP, thereby providing the driving force for transport, while the TMDs participate in substrate recognition and translocation across the lipid membrane by alternating between inward- and outward-facing conformations. By contrast, bacterial ABC exporters are typically assembled from dimers of TMD-NBD half-transporters. Thus, most bacterial ABC transporters are comprised of two identical TMDs and two identical NBDs.
Comment:All members of this ABC transporter family contain 6 alpha-helices in each transmembrane domain (TMD) for a total of 12 TM segments in the complete transporter.
Jiyao W et al.(2023). "The conserved domain database in 2023.",