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Bivalent Mical/EHBP Rab binding domain A variety of different effector proteins interact specifically with GTP-bound Rab proteins and mediate their versatile roles in membrane trafficking, including budding of vesicles from a donor membrane, directed transport through the cell and finally tethering and fusion with a target membrane. The 'bivalent Mical/EHBP Rab binding' (bMERB) domain is a Rab effector domain that is present in proteins of the Mical and EHBP families, both known to act in endosomal trafficking. The bMERB domain displays a preference for Rab8 family proteins (Rab8, 10, 13 and 15) and at least some of the bMERB domains contain two separate binding sites for Rab-proteins, allowing Micals and EHBPs to bind two Rabs simultaneously. The strong similarity between the two binding sites within one bMRB domain strongly suggests an evolutionarily development via duplication of a common ancestor supersecondary structure element. The bMERB domain has a completely alpha-helical fold consisting of a central helix and N- and C-terminal helices folding back on this central helix.
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