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 [1].

The bMERB domain has a completely α-helical fold consisting of a central helix and N- and C-terminal helices folding back on this central helix (see <PDB:5SZJ>) [1].

Some proteins known to contain a bMERB domain are listed below:

• Animal proteins of the Molecules Interacting with CasL (Mical) family, multidomain, mainly cytoplasmic, proteins, which participate in the control of actin cytoskeleton dynamics.
• Animal Eps15-homolgy (EH) domain binding proteins (EHBPs), couple vesicular transport to the actin cytoskeleton.
• Animal C16orf45 proteins.

The profile we developed covers the entire bMERB domain.