Abstract
The small GTPases Rab11, Rab14 and Rab25 regulate membrane trafficking through the recruitment of Rab11 family-interacting proteins (FIPs) to endocytic compartments. FIPs are multi-domain effector proteins that have a highly conserved Rab-binding domain (RBD) at their C-termini. Several structures of complexes of Rab11 with RBDs have previously been determined, including those of Rab11-FIP2 and Rab11-FIP3. In addition, the structures of the Rab14-FIP1 and Rab25-FIP2 complexes have been determined. All of the RBD structures contain a central parallel coiled coil in the RBD that binds to the switch 1 and switch 2 regions of the Rab. Here, the crystal structure of the uncomplexed RBD of FIP2 is presented at 2.3 Å resolution. The structure reveals antiparallel α-helices that associate through polar interactions. These include a remarkable stack of arginine residues within a four-helix bundle in the crystal lattice.
Highlights
Rab GTPases regulate membrane-trafficking pathways in eukaryotic cells via the recruitment of effector proteins to subcellular compartments (Hutagalung & Novick, 2011)
The Rab-binding domain (RBD) is shared by a family of effector proteins, which include Rab-coupling protein (RCP or FIP1), family-interacting protein 2 (FIP2) and FIP3 (Hales et al, 2001)
The N-terminus of this modular effector family is variable and consists of domains that include EF-hands, ERM domains, C2 domains and myosin V-binding domains. These effectors regulate membrane trafficking following their recruitment to subcellular compartments by Rab11, Rab14 and Rab25 GTPases
Summary
Rab GTPases regulate membrane-trafficking pathways in eukaryotic cells via the recruitment of effector proteins to subcellular compartments (Hutagalung & Novick, 2011). Rab family-interacting protein 2 (FIP2) is a 512-residue effector that contains a Rab-binding domain (RBD) at its C-terminus. The N-terminus of this modular effector family is variable and consists of domains that include EF-hands, ERM domains, C2 domains and myosin V-binding domains. These effectors regulate membrane trafficking following their recruitment to subcellular compartments by Rab, Rab and Rab GTPases. In contrast to previous crystal structures of complexes, the structure of isolated FIP2 reveals the formation of antiparallel -helical dimers that are stabilized by polar interactions
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