title: Disorder and structure in the Rab11 binding domain of Rab11 family interacting protein 2.
abstract: Rab11 plays a central role in plasma membrane recycling which returns cellular receptors for reuse at the cell surface. A recently identified family of Rab11 interacting proteins (FIP) includes FIP2. The C-terminal region of FIP2 is essential for colocalization with Rab11 on early endosomes and for enabling formation of higher-order oligomers. Rab11 binding and oligomerization of FIP2 are separable. Here we have determined the three-dimensional structure of the 40-residue coiled-coil oligomerization domain of FIP2 in the absence of Rab11 using NMR methods. The N-terminal half showed strong NOE cross-peaks and well-dispersed NMR resonances, whereas the C-terminal half had fewer NOE cross-peaks and less chemical shift dispersion. The 10 C-terminal residues were mostly disordered. The final structures of the dimer had favorable Ramachandran angles and a root-mean-square deviation of 0.59 +/- 0.13 A over superimposed backbone residues. The structure allows a comparison to a structure of FIP2 in complex with Rab11 that was determined crystallographically. In complex with Rab11, the C-terminal residues are not disordered but have a helical structure that predicts residual dipolar coupling constants that are incompatible with those measured on the unbound FIP2. In both structures, a histidine residue is found at the normally hydrophobic position of the heptad repeat of the coiled coil, and here we show its ionization destabilizes the coiled-coil structure. Together, these data allow us to build a model in which the binding of FIP family proteins to Rab11 can be described in terms of conformational changes and that suggests new modes of regulation.
authors.affiliation: Department of Biochemistry, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Wei
authors.forename: Yuqi
authors.initials: Y
authors.lastname: Liu
authors.forename: Kakoli
authors.initials: K
authors.lastname: Bose
authors.forename: Gillian D
authors.initials: GD
authors.lastname: Henry
authors.forename: James D
authors.initials: JD
authors.lastname: Baleja
mesh_terms: D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D019281:Dimerization; D006639:Histidine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D014508:Urea; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D000099193:rab11 GTP-Binding Proteins
chemical_list: D002352:Carrier Proteins; D006639:Histidine; D050505:Mutant Proteins; D010455:Peptides; D014508:Urea; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins