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. 1987 Nov 1;105(5):2203–2215. doi: 10.1083/jcb.105.5.2203

A microtubule-associated protein from Xenopus eggs that specifically promotes assembly at the plus-end

PMCID: PMC2114854  PMID: 2890645

Abstract

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 brain microtubule-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.

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Selected References

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  1. Bloom G. S., Luca F. C., Vallee R. B. Widespread cellular distribution of MAP-1A (microtubule-associated protein 1A) in the mitotic spindle and on interphase microtubules. J Cell Biol. 1984 Jan;98(1):331–340. doi: 10.1083/jcb.98.1.331. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Blose S. H., Meltzer D. I., Feramisco J. R. 10-nm filaments are induced to collapse in living cells microinjected with monoclonal and polyclonal antibodies against tubulin. J Cell Biol. 1984 Mar;98(3):847–858. doi: 10.1083/jcb.98.3.847. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Bradford M. M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem. 1976 May 7;72:248–254. doi: 10.1006/abio.1976.9999. [DOI] [PubMed] [Google Scholar]
  4. Bulinski J. C., Borisy G. G. Self-assembly of microtubules in extracts of cultured HeLa cells and the identification of HeLa microtubule-associated proteins. Proc Natl Acad Sci U S A. 1979 Jan;76(1):293–297. doi: 10.1073/pnas.76.1.293. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Cleveland D. W., Hwo S. Y., Kirschner M. W. Purification of tau, a microtubule-associated protein that induces assembly of microtubules from purified tubulin. J Mol Biol. 1977 Oct 25;116(2):207–225. doi: 10.1016/0022-2836(77)90213-3. [DOI] [PubMed] [Google Scholar]
  6. Connolly J. A., Kalnins V. I., Cleveland D. W., Kirschner M. W. Immunoflourescent staining of cytoplasmic and spindle microtubules in mouse fibroblasts with antibody to tau protein. Proc Natl Acad Sci U S A. 1977 Jun;74(6):2437–2440. doi: 10.1073/pnas.74.6.2437. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Drubin D. G., Kirschner M. W. Tau protein function in living cells. J Cell Biol. 1986 Dec;103(6 Pt 2):2739–2746. doi: 10.1083/jcb.103.6.2739. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Drubin D., Kobayashi S., Kirschner M. Association of tau protein with microtubules in living cells. Ann N Y Acad Sci. 1986;466:257–268. doi: 10.1111/j.1749-6632.1986.tb38398.x. [DOI] [PubMed] [Google Scholar]
  9. Duerr A., Pallas D., Solomon F. Molecular analysis of cytoplasmic microtubules in situ: identification of both widespread and specific proteins. Cell. 1981 Apr;24(1):203–211. doi: 10.1016/0092-8674(81)90516-x. [DOI] [PubMed] [Google Scholar]
  10. Elinson R. P. Changes in levels of polymeric tubulin associated with activation and dorsoventral polarization of the frog egg. Dev Biol. 1985 May;109(1):224–233. doi: 10.1016/0012-1606(85)90362-8. [DOI] [PubMed] [Google Scholar]
  11. Gard D. L., Kirschner M. W. A polymer-dependent increase in phosphorylation of beta-tubulin accompanies differentiation of a mouse neuroblastoma cell line. J Cell Biol. 1985 Mar;100(3):764–774. doi: 10.1083/jcb.100.3.764. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Gerhart J., Wu M., Kirschner M. Cell cycle dynamics of an M-phase-specific cytoplasmic factor in Xenopus laevis oocytes and eggs. J Cell Biol. 1984 Apr;98(4):1247–1255. doi: 10.1083/jcb.98.4.1247. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Heidemann S. R., Gallas P. T. The effect of taxol on living eggs of Xenopus laevis. Dev Biol. 1980 Dec;80(2):489–494. doi: 10.1016/0012-1606(80)90421-2. [DOI] [PubMed] [Google Scholar]
  14. Heidemann S. R., Hamborg M. A., Balasz J. E., Lindley S. Microtubules in immature oocytes of Xenopus laevis. J Cell Sci. 1985 Aug;77:129–141. doi: 10.1242/jcs.77.1.129. [DOI] [PubMed] [Google Scholar]
  15. Herzog W., Weber K. Fractionation of brain microtubule-associated proteins. Isolation of two different proteins which stimulate tubulin polymerization in vitro. Eur J Biochem. 1978 Dec 1;92(1):1–8. doi: 10.1111/j.1432-1033.1978.tb12716.x. [DOI] [PubMed] [Google Scholar]
  16. Izant J. G., McIntosh J. R. Microtubule-associated proteins: a monoclonal antibody to MAP2 binds to differentiated neurons. Proc Natl Acad Sci U S A. 1980 Aug;77(8):4741–4745. doi: 10.1073/pnas.77.8.4741. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Jessus C., Thibier C., Ozon R. Identification of microtubule-associated proteins (MAPs) in Xenopus oocyte. FEBS Lett. 1985 Nov 11;192(1):135–140. doi: 10.1016/0014-5793(85)80059-4. [DOI] [PubMed] [Google Scholar]
  18. Karsenti E., Bravo R., Kirschner M. Phosphorylation changes associated with the early cell cycle in Xenopus eggs. Dev Biol. 1987 Feb;119(2):442–453. doi: 10.1016/0012-1606(87)90048-0. [DOI] [PubMed] [Google Scholar]
  19. Karsenti E., Newport J., Hubble R., Kirschner M. Interconversion of metaphase and interphase microtubule arrays, as studied by the injection of centrosomes and nuclei into Xenopus eggs. J Cell Biol. 1984 May;98(5):1730–1745. doi: 10.1083/jcb.98.5.1730. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Kim H., Binder L. I., Rosenbaum J. L. The periodic association of MAP2 with brain microtubules in vitro. J Cell Biol. 1979 Feb;80(2):266–276. doi: 10.1083/jcb.80.2.266. [DOI] [PMC free article] [PubMed] [Google Scholar]
  21. Maller J., Wu M., Gerhart J. C. Changes in protein phosphorylation accompanying maturation of Xenopus laevis oocytes. Dev Biol. 1977 Jul 15;58(2):295–312. doi: 10.1016/0012-1606(77)90093-8. [DOI] [PubMed] [Google Scholar]
  22. Manes M. E., Barbieri F. D. On the possibility of sperm aster involvement in dorso-ventral polarization and pronuclear migration in the amphibian egg. J Embryol Exp Morphol. 1977 Aug;40:187–197. [PubMed] [Google Scholar]
  23. Miake-Lye R., Newport J., Kirschner M. Maturation-promoting factor induces nuclear envelope breakdown in cycloheximide-arrested embryos of Xenopus laevis. J Cell Biol. 1983 Jul;97(1):81–91. doi: 10.1083/jcb.97.1.81. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Mitchison T., Kirschner M. Dynamic instability of microtubule growth. Nature. 1984 Nov 15;312(5991):237–242. doi: 10.1038/312237a0. [DOI] [PubMed] [Google Scholar]
  25. Mitchison T., Kirschner M. Microtubule assembly nucleated by isolated centrosomes. Nature. 1984 Nov 15;312(5991):232–237. doi: 10.1038/312232a0. [DOI] [PubMed] [Google Scholar]
  26. Newport J., Kirschner M. A major developmental transition in early Xenopus embryos: I. characterization and timing of cellular changes at the midblastula stage. Cell. 1982 Oct;30(3):675–686. doi: 10.1016/0092-8674(82)90272-0. [DOI] [PubMed] [Google Scholar]
  27. Olmsted J. B. Microtubule-associated proteins. Annu Rev Cell Biol. 1986;2:421–457. doi: 10.1146/annurev.cb.02.110186.002225. [DOI] [PubMed] [Google Scholar]
  28. Vallee R. B. A taxol-dependent procedure for the isolation of microtubules and microtubule-associated proteins (MAPs). J Cell Biol. 1982 Feb;92(2):435–442. doi: 10.1083/jcb.92.2.435. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Vallee R. B., Bloom G. S. Isolation of sea urchin egg microtubules with taxol and identification of mitotic spindle microtubule-associated proteins with monoclonal antibodies. Proc Natl Acad Sci U S A. 1983 Oct;80(20):6259–6263. doi: 10.1073/pnas.80.20.6259. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Wu M., Gerhart J. C. Partial purification and characterization of the maturation-promoting factor from eggs of Xenopus laevis. Dev Biol. 1980 Oct;79(2):465–477. doi: 10.1016/0012-1606(80)90131-1. [DOI] [PubMed] [Google Scholar]

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