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Cation efflux system protein CusB domain 1 The cation efflux system protein CusB from E. coli can be divided into four different domains, the first three domains of the protein are mostly beta-strands and the fourth forms an all alpha-helical domain. This entry represents the first beta-domain (domain 1) of CusB and it is formed by the N and C-terminal ends of the polypeptide (residues 89-102 and 324-385). CusB is part of the copper-transporting efflux system CusCFBA. This domain can also be found in other membrane-fusion proteins, such as HlyD, MdtN, MdtE and AaeA. HlyD is a component of the prototypical alpha-haemolysin (HlyA) bacterial type I secretion system, along with the other components HlyB and TolC. HlyD is anchored in the cytoplasmic membrane by a single transmembrane domain and has a large periplasmic domain within the carboxy-terminal 100 amino acids, HlyB and HlyD form a stable complex that binds the recombinant protein bearing a C-terminal HlyA signal sequence and ATP in the cytoplasm. HlyD, HlyB and TolC combine to form the three-component ABC transporter complex that forms a trans-membrane channel or pore through which HlyA can be transferred directly to the extracellular medium. Cutinase has been shown to be transported effectively through this pore.
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