Tubulin folding cofactors as GTPase-activating proteins. GTP hydrolysis and the assembly of the alpha/beta-tubulin heterodimer - PubMed (original) (raw)

. 1999 Aug 20;274(34):24054-8.

doi: 10.1074/jbc.274.34.24054.

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Tubulin folding cofactors as GTPase-activating proteins. GTP hydrolysis and the assembly of the alpha/beta-tubulin heterodimer

G Tian et al. J Biol Chem. 1999.

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Abstract

In vivo, many proteins must interact with molecular chaperones to attain their native conformation. In the case of tubulin, newly synthesized alpha- and beta-subunits are partially folded by cytosolic chaperonin, a double-toroidal ATPase with homologs in all kingdoms of life and in most cellular compartments. alpha- and beta-tubulin folding intermediates are then brought together by tubulin-specific chaperone proteins (named cofactors A-E) in a cofactor-containing supercomplex with GTPase activity. Here we show that tubulin subunit exchange can only occur by passage through this supercomplex, thus defining it as a dimer-making machine. We also show that hydrolysis of GTP by beta-tubulin in the supercomplex acts as a switch for the release of native tubulin heterodimer. In this folding reaction and in the related reaction of tubulin-folding cofactors with native tubulin, the cofactors behave as GTPase-activating proteins, stimulating the GTP-binding protein beta-tubulin to hydrolyze its GTP.

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