title: Crystal structure of the intraflagellar transport complex 25/27.
abstract: The cilium is an important organelle that is found on many eukaryotic cells, where it serves essential functions in motility, sensory reception and signalling. Intraflagellar transport (IFT) is a vital process for the formation and maintenance of cilia. We have determined the crystal structure of Chlamydomonas reinhardtii IFT25/27, an IFT sub-complex, at 2.6 Å resolution. IFT25 and IFT27 interact via a conserved interface that we verify biochemically using structure-guided mutagenesis. IFT27 displays the fold of Rab-like small guanosine triphosphate hydrolases (GTPases), binds GTP and GDP with micromolar affinity and has very low intrinsic GTPase activity, suggesting that it likely requires a GTPase-activating protein (GAP) for robust GTP turnover. A patch of conserved surface residues contributed by both IFT25 and IFT27 is found adjacent to the GTP-binding site and could mediate the binding to other IFT proteins as well as to a potential GAP. These results provide the first step towards a high-resolution structural understanding of the IFT complex.
authors.affiliation: Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany.
authors.forename: Sagar
authors.initials: S
authors.lastname: Bhogaraju
authors.forename: Michael
authors.initials: M
authors.lastname: Taschner
authors.forename: Michaela
authors.initials: M
authors.lastname: Morawetz
authors.forename: Claire
authors.initials: C
authors.lastname: Basquin
authors.forename: Esben
authors.initials: E
authors.lastname: Lorentzen
mesh_terms: D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D004252:DNA Mutational Analysis; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D020836:Protein Structure, Quaternary; D017386:Sequence Homology, Amino Acid
chemical_list: D002352:Carrier Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate