A purified Drosophila septin complex forms filaments and exhibits GTPase activity.
Septin proteins are necessary for cytokinesis in budding yeast and Drosophila and are thought to be the subunits of the yeast neck filaments. To test whether septins actually form filaments, an immunoaffinity approach was used to isolate a septin complex from Drosophila embryos. The purified complex is comprised of the three previously identified septin polypeptides Pnut, Sep2, and Sep1. Hydrodynamic and sequence data suggest that the complex is composed of a heterotrimer of homodimers. The complex copurifies with one molecule of bound guanine nucleotide per septin polypeptide. It binds and hydrolyzes exogenously added GTP. These observations together with conserved sequence motifs identify the septins as members of the GTPase superfamily. We discuss a model of filament structure and speculate as to how the filaments are organized within cells.
Field
C M
CM
Department of Biochemistry and Biophysics, University of California at San Francisco 94143-0448, USA. cfield@socrates.ucsf.edu
al-Awar
O
O
Rosenblatt
J
J
Wong
M L
ML
Alberts
B
B
Mitchison
T J
TJ
D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D003851:Deoxyribonucleases / Q000302:isolation & purification / Q000378:metabolism*; D004330:Drosophila / Q000201:enzymology*; D029721:Drosophila Proteins; D005095:Exoribonucleases; D005656:Fungal Proteins / Q000302:isolation & purification / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D008840:Microfilament Proteins; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D011506:Proteins / Q000302:isolation & purification / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins
D029721:Drosophila Proteins; D005656:Fungal Proteins; D008840:Microfilament Proteins; D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; C087195:pnut protein, Drosophila; D006160:Guanosine Triphosphate; D003851:Deoxyribonucleases; D005095:Exoribonucleases; C068398:XRN1 protein, S cerevisiae; D020558:GTP Phosphohydrolases