Domain analysis of cortexillin I: actin-bundling, PIP(2)-binding and the rescue of cytokinesis.
Cortexillins are actin-bundling proteins that form a parallel two-stranded coiled-coil rod. Actin-binding domains of the alpha-actinin/spectrin type are located N-terminal to the rod and unique sequence elements are found in the C-terminal region. Domain analysis in vitro revealed that the N-terminal domains are not responsible for the strong actin-filament bundling activity of cortexillin I. The strongest activity resides in the C-terminal region. Phosphatidylinositol 4,5-bisphosphate (PIP(2)) suppresses this bundling activity by binding to a C-terminal nonapeptide sequence. These data define a new PIP(2)-regulated actin-bundling site. In vivo the PIP(2)-binding motif enhances localization of a C-terminal cortexillin I fragment to the cell cortex and improves the rescue of cytokinesis. This motif is not required, however, for translocation to the cleavage furrow. A model is presented proposing that cortexillin translocation is based on a mitotic cycle of polar actin polymerization and midzone depolymerization.
Stock
A
A
Max-Planck-Institut für Biochemie, Am Klopferspitz 18a, D-82152 Martinsried, Germany.
Steinmetz
M O
MO
Janmey
P A
PA
Aebi
U
U
Gerisch
G
G
Kammerer
R A
RA
Weber
I
I
Faix
J
J
D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D002453:Cell Cycle; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011485:Protein Binding; D015800:Protozoan Proteins; D011817:Rabbits
D000199:Actins; D008840:Microfilament Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D015800:Protozoan Proteins; C101109:ctxA protein, Dictyostelium discoideum