Editing ABC transporter (section)

=== Sav1866 ===
The first high-resolution structure reported for an ABC exporter was that of Sav1866 (3.A.1.106.2) from ''Staphylococcus aureus''.<ref name=pohl/><ref>{{cite journal | vauthors = Dawson RJ, Locher KP | title = Structure of the multidrug ABC transporter Sav1866 from Staphylococcus aureus in complex with AMP-PNP | journal = FEBS Letters | volume = 581 | issue = 5 | pages = 935–8 | date = Mar 2007 | pmid = 17303126 | doi = 10.1016/j.febslet.2007.01.073 | s2cid = 19960736 | url = https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A17836 | doi-access =  | bibcode = 2007FEBSL.581..935D }}</ref> Sav1866 is a homolog of multidrug ABC transporters. It shows significant sequence similarity to human ABC transporters of subfamily B that includes MDR1 and TAP1/TAP2. The ATPase activity of Sav1866 is known to be stimulated by cancer drugs such as [[doxorubicin]], [[vinblastine]] and others,<ref name=velamakanni2008>{{cite journal | vauthors = Velamakanni S, Yao Y, Gutmann DA, van Veen HW | title = Multidrug transport by the ABC transporter Sav1866 from Staphylococcus aureus | journal = Biochemistry | volume = 47 | issue = 35 | pages = 9300–8 | date = Sep 2008 | pmid = 18690712 | doi = 10.1021/bi8006737 }}</ref> which suggests similar substrate specificity to P-glycoprotein and therefore a possible common mechanism of substrate translocation. Sav1866 is a homodimer of half transporters, and each subunit contains an N-terminal TMD with six helices and a C-terminal NBD. The NBDs are similar in structure to those of other ABC transporters, in which the two ATP binding sites are formed at the dimer interface between the Walker A motif of one NBD and the LSGGQ motif of the other. The ADP-bound structure of Sav1866 shows the NBDs in a closed dimer and the TM helices split into two "wings" oriented towards the periplasm, forming the outward-facing conformation. Each wing consists of helices TM1-2 from one subunit and TM3-6 from the other subunit. It contains long intracellular loops (ICLs or ICD) connecting the TMDs that extend beyond the lipid bilayer into the cytoplasm and interacts with the 8=D. Whereas the importers contain a short coupling helix that contact a single NBD, Sav1866 has two intracellular coupling helices, one (ICL1) contacting the NBDs of both subunits and the other (ICL2) interacting with only the opposite NBD subunit.<ref name=rees/><ref name=sav1866/><ref name=oldham2008/>