ATP-binding cassette domain of the polyamine transporter
PotA is an ABC-type transporter and the ATPase component of the spermidine/putrescine-preferential uptake system consisting of PotA, -B, -C, and -D. PotA has two domains with the N-terminal domain containing the ATPase activity and the residues required for homodimerization with PotA and heterdimerization with PotB. ABC transporters are a large family of proteins involved in the transport of a wide variety of different compounds, like sugars, ions, peptides, and more complex organic molecules. The nucleotide binding domain shows the highest similarity between all members of the family. ABC transporters are a subset of nucleotide hydrolases that contain a signature motif, Q-loop, and H-loop/switch region, in addition to, the Walker A motif/P-loop and Walker B motif commonly found in a number of ATP- and GTP-binding and hydrolyzing proteins.