ROLE OF 300-KDA COMPLEXES AS INTERMEDIATES IN TUBULIN FOLDING AND DIMERIZATION - CHARACTERIZATION OF A 25-KDA CYTOSOLIC PROTEIN INVOLVED INTHE GTP-DEPENDENT RELEASE OF MONOMERIC TUBULIN
R. Paciucci, ROLE OF 300-KDA COMPLEXES AS INTERMEDIATES IN TUBULIN FOLDING AND DIMERIZATION - CHARACTERIZATION OF A 25-KDA CYTOSOLIC PROTEIN INVOLVED INTHE GTP-DEPENDENT RELEASE OF MONOMERIC TUBULIN, Biochemical journal, 301, 1994, pp. 105-110
beta-Tubulin synthesized in vitro in rabbit reticulocyte lysate is fou
nd associated with 900 kDa complexes (C900) containing T Complex Polyp
eptide 1 (TCP1), heat-shock protein (hsp) 70 and other unidentified pr
oteins, with smaller 300 kDa complexes (C300) of unknown nature, in di
meric association with reticulocyte alpha-tubulin and in monomeric for
ms. Pulse-chase experiments indicated that production of fully functio
nal beta-tubulin was preceded by its association with C900 and C300 mu
ltimolecular complexes and by the appearance of beta-monomers. The hig
h-molecular-mass forms appeared as intermediate products in the proces
s leading to fully functional dimerizable beta-tubulin. C300-associate
d tubulin can be released as beta-monomer by addition of a cofactor pr
esent in reticulocyte lysate. Here a 25 kDa protein which releases tub
ulin monomers from C300 has been identified and characterized. The pro
tein specifically released monomers from C300, but not from C900, in a
process favoured by GTP.