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Mol Cell Biol. 2002 Jan;22(1):138-47.

Protection from free beta-tubulin by the beta-tubulin binding protein Rbl2p.

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  • 1Department of Biology and Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

Abstract

Free beta-tubulin not in heterodimers with alpha-tubulin can be toxic, disrupting microtubule assembly and function. We are interested in the mechanisms by which cells protect themselves from free beta-tubulin. This study focused specifically on the function of Rbl2p, which, like alpha-tubulin, can rescue cells from free beta-tubulin. In vitro studies of the mammalian homolog of Rbl2p, cofactor A, have suggested that Rbl2p/cofactor A may be involved in tubulin folding. Here we show that Rbl2p becomes essential in cells containing a modest excess of beta-tubulin relative to alpha-tubulin. However, this essential activity of Rbl2p/cofactorA does not depend upon the reactions described by the in vitro assay. Rescue of beta-tubulin toxicity requires a minimal but substoichiometric ratio of Rbl2p to beta-tubulin. The data suggest that Rbl2p binds transiently to free beta-tubulin, which then passes into an aggregated form that is not toxic.

PMID:
11739729
[PubMed - indexed for MEDLINE]
PMCID:
PMC134216
Free PMC Article
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