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We have isolated a protein factor from Xenopus eggs that promotes microtubule assembly in vitro. Assembly promotion was associated with a 215-kD protein after a 1,000-3,000-fold enrichment of activity. The 215-kD protein, termed Xenopus microtubule assembly protein (XMAP), binds to microtubules with a stoichiometry of 0.06 mol/mol tubulin dimer. XMAP is immunologically distinct from the Xenopus homologues to mammalian brainmicrotubule-associated proteins; however, protein species immunologically related to XMAP with different molecular masses are found in Xenopus neuronal tissues and testis. XMAP is unusual in that it specifically promotes microtubule assembly at the plus-end. At a molar ratio of 0.01 mol XMAP/mol tubulin the assembly rate of the microtubule plus-end is accelerated 8-fold while the assembly rate of the minus-end is increased only 1.8-fold. Under these conditions XMAP promotes a 10-fold increase in the on-rate constant (from 1.4 s-1.microM-1 for microtubules assembled from pure tubulin to 15 s-1.microM-1), and a 10-fold decrease in off-rate constant (from 340 to 34 s-1). Given its stoichiometry in vivo, XMAP must be the major microtubule assembly factor in the Xenopus egg. XMAP is phosphorylated during M-phase of both meiotic and mitotic cycles, suggesting that its activity may be regulated during the cell cycle.
Bloom,
Widespread cellular distribution of MAP-1A (microtubule-associated protein 1A) in the mitotic spindle and on interphase microtubules.
1984, Pubmed
Bloom,
Widespread cellular distribution of MAP-1A (microtubule-associated protein 1A) in the mitotic spindle and on interphase microtubules.
1984,
Pubmed Blose,
10-nm filaments are induced to collapse in living cells microinjected with monoclonal and polyclonal antibodies against tubulin.
1984,
Pubmed Bradford,
A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding.
1976,
Pubmed Bulinski,
Self-assembly of microtubules in extracts of cultured HeLa cells and the identification of HeLa microtubule-associated proteins.
1979,
Pubmed Cleveland,
Purification of tau, a microtubule-associated protein that induces assembly of microtubules from purified tubulin.
1977,
Pubmed Connolly,
Immunoflourescent staining of cytoplasmic and spindle microtubules in mouse fibroblasts with antibody to tau protein.
1977,
Pubmed Drubin,
Association of tau protein with microtubules in living cells.
1986,
Pubmed Drubin,
Tau protein function in living cells.
1986,
Pubmed Duerr,
Molecular analysis of cytoplasmic microtubules in situ: identification of both widespread and specific proteins.
1981,
Pubmed Elinson,
Changes in levels of polymeric tubulin associated with activation and dorsoventral polarization of the frog egg.
1985,
Pubmed
,
Xenbase Gard,
A polymer-dependent increase in phosphorylation of beta-tubulin accompanies differentiation of a mouse neuroblastoma cell line.
1985,
Pubmed Gerhart,
Cell cycle dynamics of an M-phase-specific cytoplasmic factor in Xenopus laevis oocytes and eggs.
1984,
Pubmed
,
Xenbase Heidemann,
The effect of taxol on living eggs of Xenopus laevis.
1980,
Pubmed
,
Xenbase Heidemann,
Microtubules in immature oocytes of Xenopus laevis.
1985,
Pubmed
,
Xenbase Herzog,
Fractionation of brain microtubule-associated proteins. Isolation of two different proteins which stimulate tubulin polymerization in vitro.
1978,
Pubmed Izant,
Microtubule-associated proteins: a monoclonal antibody to MAP2 binds to differentiated neurons.
1980,
Pubmed Jessus,
Identification of microtubule-associated proteins (MAPs) in Xenopus oocyte.
1985,
Pubmed
,
Xenbase Karsenti,
Phosphorylation changes associated with the early cell cycle in Xenopus eggs.
1987,
Pubmed
,
Xenbase Karsenti,
Interconversion of metaphase and interphase microtubule arrays, as studied by the injection of centrosomes and nuclei into Xenopus eggs.
1984,
Pubmed
,
Xenbase Kim,
The periodic association of MAP2 with brain microtubules in vitro.
1979,
Pubmed Maller,
Changes in protein phosphorylation accompanying maturation of Xenopus laevis oocytes.
1977,
Pubmed
,
Xenbase Manes,
On the possibility of sperm aster involvement in dorso-ventral polarization and pronuclear migration in the amphibian egg.
1977,
Pubmed Miake-Lye,
Maturation-promoting factor induces nuclear envelope breakdown in cycloheximide-arrested embryos of Xenopus laevis.
1983,
Pubmed
,
Xenbase Mitchison,
Dynamic instability of microtubule growth.
,
Pubmed Mitchison,
Microtubule assembly nucleated by isolated centrosomes.
,
Pubmed Newport,
A major developmental transition in early Xenopus embryos: I. characterization and timing of cellular changes at the midblastula stage.
1982,
Pubmed
,
Xenbase Olmsted,
Microtubule-associated proteins.
1986,
Pubmed Vallee,
A taxol-dependent procedure for the isolation of microtubules and microtubule-associated proteins (MAPs).
1982,
Pubmed Vallee,
Isolation of sea urchin egg microtubules with taxol and identification of mitotic spindle microtubule-associated proteins with monoclonal antibodies.
1983,
Pubmed Wu,
Partial purification and characterization of the maturation-promoting factor from eggs of Xenopus laevis.
1980,
Pubmed
,
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