Formation and function of the Rbl2p-beta-tubulin complex.
The yeast protein Rbl2p suppresses the deleterious effects of excess beta-tubulin as efficiently as does alpha-tubulin. Both in vivo and in vitro, Rbl2p forms a complex with beta-tubulin that does not contain alpha-tubulin, thus defining a second pool of beta-tubulin in the cell. Formation of the complex depends upon the conformation of beta-tubulin. Newly synthesized beta-tubulin can bind to Rbl2p before it binds to alpha-tubulin. Rbl2p can also bind beta-tubulin from the alpha/beta-tubulin heterodimer, apparently by competing with alpha-tubulin. The Rbl2p-beta-tubulin complex has a half-life of approximately 2.5 h and is less stable than the alpha/beta-tubulin heterodimer. The results of our experiments explain both how excess Rbl2p can rescue cells overexpressing beta-tubulin and how it can be deleterious in a wild-type background. They also suggest that the Rbl2p-beta-tubulin complex is part of a cellular mechanism for regulating the levels and dimerization of tubulin chains.
Archer
J E
JE
Department of Biology and Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139, USA.
Magendantz
M
M
Vega
L R
LR
Solomon
F
F
D019281:Dimerization; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D006639:Histidine / Q000096:biosynthesis / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics; D014404:Tubulin / Q000378:metabolism*
D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D014404:Tubulin; D006639:Histidine