Abruzzi Katharine C, Smith Adelle, Chen William, Solomon Frank
Department of Biology and Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Mol Cell Biol. 2002 Jan;22(1):138-47. doi: 10.1128/MCB.22.1.138-147.2002.
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.
未与α-微管蛋白形成异二聚体的游离β-微管蛋白可能具有毒性，会破坏微管的组装和功能。我们对细胞保护自身免受游离β-微管蛋白影响的机制感兴趣。本研究特别关注Rbl2p的功能，它与α-微管蛋白一样，能够拯救细胞免受游离β-微管蛋白的影响。对Rbl2p的哺乳动物同源物辅因子A的体外研究表明，Rbl2p/辅因子A可能参与微管蛋白折叠。我们在此表明，在相对于α-微管蛋白含有适度过量β-微管蛋白的细胞中，Rbl2p变得至关重要。然而，Rbl2p/辅因子A的这种关键活性并不依赖于体外测定所描述的反应。拯救β-微管蛋白毒性需要Rbl2p与β-微管蛋白的比例最小但低于化学计量。数据表明，Rbl2p与游离β-微管蛋白短暂结合，然后β-微管蛋白转变为无毒的聚集形式。
