Journal article
Purification and characterization of ensconsin, a novel microtubule stabilizing protein
Journal of cell science, Vol.107(10), pp.2839-2849
10/1994
DOI: 10.1242/jcs.107.10.2839
PMID: 7876351
Abstract
In previous studies (Bulinski and Borisy (1979). Proc. Nat. Acad. Sci. 76, 293-297; Weatherbee et al. (1980). Biochemistry 19, 4116-4123) a microtubule-associated protein (MAP) of M(r) approximately 125,000 was identified as a prominent MAP in HeLa cells. We set out to perform a biochemical characterization of this protein, and to determine its in vitro functions and in vivo distribution. We determined that, like the assembly-promoting MAPs, tau, MAP2 and MAP4, the 125 kDa MAP was both proteolytically sensitive and thermostable. An additional property of this MAP; namely, its unusually tight association with a calcium-insensitive population of MTs in the presence of taxol, was exploited in devising an efficient purification strategy. Because of the MAP's tenacious association with a stable population of MTs, and because it appeared to contribute to the stability of this population of MTs in vitro, we have named this protein ensconsin. We examined the binding of purified ensconsin to MTs; ensconsin exhibited binding that saturated its MT binding sites at an approximate molar ratio of 1:6 (ensconsin:tubulin). Unlike other MAPs characterized to date, ensconsin's binding to MTs was insensitive to moderate salt concentrations (< or = 0.6 M). We further characterized ensconsin in immunoblotting experiments using mouse polyclonal anti-ensconsin antibodies and antibodies reactive with previously described MAPs, such as high molecular mass tau isoforms, dynamin, STOP, CLIP-170 and kinesin. These experiments demonstrated that ensconsin is distinct from other proteins of similar M(r) that may be present in association with MTs. Immunofluorescence with anti-ensconsin antibodies demonstrated that ensconsin was detectable in association with most or all of the MTs of several lines of human epithelial, fibroblastic and muscle cells; its in vivo properties and distribution, especially in response to drug or other treatments of cells, were found to be different from those of MAP4, the predominant MAP found in these cell types. We conclude that ensconsin, a MAP found in a variety of human cells, is biochemically - and perhaps functionally - distinct from other MAPs present in non-neuronal cells.
Details
- Title: Subtitle
- Purification and characterization of ensconsin, a novel microtubule stabilizing protein
- Creators
- J C Bulinski - Department of Anatomy and Cell Biology, Columbia University, College of Physicians & Surgeons, New York, NY 10032A Bossler
- Resource Type
- Journal article
- Publication Details
- Journal of cell science, Vol.107(10), pp.2839-2849
- Publisher
- England
- DOI
- 10.1242/jcs.107.10.2839
- PMID
- 7876351
- ISSN
- 0021-9533
- eISSN
- 1477-9137
- Grant note
- CA39755 / NCI NIH HHS
- Language
- English
- Date published
- 10/1994
- Academic Unit
- Pathology
- Record Identifier
- 9984047708302771
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