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| MalFGK2-MBP
maltose uptake transporter This is a Type I importer found only in prokaryotes. It has an outward-facing conformation with MBP. It's bound with ADP-VO43-, Mg2+ and maltose with a resolution of 2.40. It contains four domains, two NBDs MalK dimer and two TMDs MalF and MalG. Addionally, it includes a periplasmic maltose-binding protein (MBP). So it is substrate selective. Snapshots of the maltose transporter during ATP hydrolysis. Oldham, M.L., and J. Chen. 2011b.(PubMed) 3PUV (PDB) |
Multidrug transporter P-glycoprotein (Mus
musculus)
This is an ABC exporter. It has a re-refined inward-facing conformation with a resolution of 3.80. It also has four domains, two NBDs and two TMDs. But all the domains are from one polypeptide chain.It has no substrate binding proteins (SBPs) like MBP of MalFGK2-MBP. It possible that the structural differences between ABC exporters and importers are related to the opposing directions in which the substrate is pumped and the range of tranported substrates. ABC exporters are involved in the export of hydrophobic compounds while importers are selective for a single or a few related water-soluable substrates. Another major difference between these two transporters is the TMDs (not shown). Refined structures of mouse P-glycoprotein. Li, J., K. F.Jaimes, and S.G. Aller. 2014(PubMed) 4M1M (PDB) |