title: Functional insight into the role of Orc6 in septin complex filament formation in Drosophila.
abstract: Septins belong to a family of polymerizing GTP-binding proteins that are important for cytokinesis and other processes that involve spatial organization of the cell cortex. We reconstituted a recombinant Drosophila septin complex and compared activities of the wild-type and several mutant septin complex variants both in vitro and in vivo. We show that Drosophila septin complex functions depend on the intact GTP-binding and/or hydrolysis domains of Pnut, Sep1, and Sep2. The presence of the functional C-terminal domain of septins is required for the integrity of the complex. Drosophila Orc6 protein, the smallest subunit of the origin recognition complex (ORC), directly binds to septin complex and facilitates septin filament formation. Orc6 forms dimers through the interactions of its N-terminal, TFIIB-like domains. This ability of the protein suggests a direct bridging role for Orc6 in stimulating septin polymerization in Drosophila. Studies reported here provide a functional dissection of a Drosophila septin complex and highlight the basic conserved and divergent features among metazoan septin complexes.
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham School of Medicine, Birmingham, AL 35294 Institute of Cytology and Genetics, Novosibirsk 630090, Russia.
authors.forename: Katarina
authors.initials: K
authors.lastname: Akhmetova
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham School of Medicine, Birmingham, AL 35294.
authors.forename: Maxim
authors.initials: M
authors.lastname: Balasov
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham School of Medicine, Birmingham, AL 35294.
authors.forename: Richard P H
authors.initials: RP
authors.lastname: Huijbregts
authors.affiliation: Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham School of Medicine, Birmingham, AL 35294 ichesnokov@uab.edu.
authors.forename: Igor
authors.initials: I
authors.lastname: Chesnokov
mesh_terms: D000818:Animals; D048749:Cytokinesis / Q000502:physiology; D003593:Cytoplasm / Q000502:physiology; D003599:Cytoskeleton / Q000502:physiology; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D031541:Fluorescence Resonance Energy Transfer; D005838:Genotype; D006868:Hydrolysis; D008854:Microscopy, Electron; D009154:Mutation; D051738:Origin Recognition Complex / Q000235:genetics / Q000378:metabolism*; D055503:Protein Multimerization; D058112:Septins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D029721:Drosophila Proteins; C477598:ORC6 protein, Drosophila; C497227:ORC6 protein, human; D051738:Origin Recognition Complex; D058112:Septins