title: Drosophila melanogaster mini spindles TOG3 utilizes unique structural elements to promote domain stability and maintain a TOG1- and TOG2-like tubulin-binding surface.
abstract: Microtubule-associated proteins regulate microtubule (MT) dynamics spatially and temporally, which is essential for proper formation of the bipolar mitotic spindle. The XMAP215 family is comprised of conserved microtubule-associated proteins that use an array of tubulin-binding tumor overexpressed gene (TOG) domains, consisting of six (A-F) Huntingtin, elongation factor 3, protein phosphatase 2A, target of rapamycin (HEAT) repeats, to robustly increase MT plus-end polymerization rates. Recent work showed that TOG domains have differentially conserved architectures across the array, with implications for position-dependent TOG domain tubulin binding activities and function within the XMAP215 MT polymerization mechanism. Although TOG domains 1, 2, and 4 are well described, structural and mechanistic information characterizing TOG domains 3 and 5 is outstanding. Here, we present the structure and characterization of Drosophila melanogaster Mini spindles (Msps) TOG3. Msps TOG3 has two unique features as follows: the first is a C-terminal tail that stabilizes the ultimate four HEAT repeats (HRs), and the second is a unique architecture in HR B. Structural alignments of TOG3 with other TOG domain structures show that the architecture of TOG3 is most similar to TOG domains 1 and 2 and diverges from TOG4. Docking TOG3 onto recently solved Stu2 TOG1· and TOG2·tubulin complex structures suggests that TOG3 uses similarly conserved tubulin-binding intra-HEAT loop residues to engage α- and β-tubulin. This indicates that TOG3 has maintained a TOG1- and TOG2-like TOG-tubulin binding mode despite structural divergence. The similarity of TOG domains 1-3 and the divergence of TOG4 suggest that a TOG domain array with polarized structural diversity may play a key mechanistic role in XMAP215-dependent MT polymerization activity.
authors.affiliation: From the Department of Biochemistry and Biophysics, Program in Molecular and Cellular Biophysics, and.
authors.forename: Amy E
authors.initials: AE
authors.lastname: Howard
authors.affiliation: From the Department of Biochemistry and Biophysics, Program in Molecular and Cellular Biophysics, and.
authors.forename: Jaime C
authors.initials: JC
authors.lastname: Fox
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599 kslep@bio.unc.edu.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Slep
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018360:Crystallography, X-Ray; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D008869:Microtubule-Associated Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008870:Microtubules / Q000737:chemistry* / Q000378:metabolism; D008938:Mitosis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D058105:Polymerization; D011485:Protein Binding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055550:Protein Stability; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D008941:Spindle Apparatus / Q000737:chemistry* / Q000378:metabolism; D014404:Tubulin / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D008869:Microtubule-Associated Proteins; D020033:Protein Isoforms; D014404:Tubulin
keywords: Cell Division; Crystal Structure; Microtubule; Microtubule Dynamics; Microtubule-associated Protein; Msps; Structural Biology; TOG; Tubulin; XMAP215