title: Intraflagellar transport proteins 172, 80, 57, 54, 38, and 20 form a stable tubulin-binding IFT-B2 complex.
abstract: Intraflagellar transport (IFT) relies on the IFT complex and is required for ciliogenesis. The IFT-B complex consists of 9-10 stably associated core subunits and six "peripheral" subunits that were shown to dissociate from the core structure at moderate salt concentration. We purified the six "peripheral"IFT-B subunits of Chlamydomonas reinhardtiias recombinant proteins and show that they form a stable complex independently of the IFT-B core. We suggest a nomenclature of IFT-B1 (core) and IFT-B2 (peripheral) for the two IFT-B subcomplexes. We demonstrate that IFT88, together with the N-terminal domain of IFT52, is necessary to bridge the interaction between IFT-B1 and B2. The crystal structure of IFT52N reveals highly conserved residues critical for IFT-B1/IFT-B2 complex formation. Furthermore, we show that of the three IFT-B2 subunits containing a calponin homology (CH) domain (IFT38, 54, and 57), only IFT54 binds αβ-tubulin as a potential IFT cargo, whereas the CH domains of IFT38 and IFT57 mediate the interaction with IFT80 and IFT172, respectively. Crystal structures of IFT54 CH domains reveal that tubulin binding is mediated by basic surface-exposed residues.
authors.affiliation: Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Taschner
authors.affiliation: Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany.
authors.forename: Kristina
authors.initials: K
authors.lastname: Weber
authors.affiliation: Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany.
authors.forename: André
authors.initials: A
authors.lastname: Mourão
authors.affiliation: Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Vetter
authors.affiliation: Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany.
authors.forename: Mayanka
authors.initials: M
authors.lastname: Awasthi
authors.affiliation: Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Stiegler
authors.affiliation: Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany.
authors.forename: Sagar
authors.initials: S
authors.lastname: Bhogaraju
authors.affiliation: Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Martinsried, Germany lorentze@biochem.mpg.de.
authors.forename: Esben
authors.initials: E
authors.lastname: Lorentzen
mesh_terms: D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D018360:Crystallography, X-Ray; D005407:Flagella / Q000378:metabolism*; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D014404:Tubulin
keywords: IFT54; IFT‐B; cilia; intraflagellar transport; tubulin transpor