Send to

Choose Destination
Biochemistry. 1996 Dec 10;35(49):15870-82.

Newly-synthesized beta-tubulin demonstrates domain-specific interactions with the cytosolic chaperonin.

Author information

Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio 44106, USA.


Tubulin folding requires two chaperone systems, i.e., the 900 kDa cytosolic chaperonin referred to as the TCP-1 complex or TRiC which facilitates folding of the alpha- and beta-tubulin subunits and a ca. 180 kDa complex which facilitates further assembly into heterodimer. beta-Tubulin mutants were expressed in rabbit reticulocyte lysates, and the effect of C-terminal, N-terminal, and internal deletions on the binding of beta-tubulin polypeptides to the 900 and 180 kDa complexes was ascertained. Proteolytic studies of chaperonin-bound beta-tubulin were also implemented. These studies support the concept of quasi-native chaperonin-bound intermediates [Tian et al. J. Biol. Chem. (1995) 270, 1-4]. Three "domains" similar in size to the domains in the native protein were implicated in facilitated folding: i.e., an internal or "M-domain" composed of residues approximately 140-260 which binds to TRiC; a "C-domain" composed of residues approximately 300-445 which interacts less strongly with TRiC and may contain regulatory sequences for tubulin release from the chaperonin; and an "N-domain" composed of residues approximately 1-140 which apparently does not interact with TRiC but does interact with the 180 kDa complex. The major TRiC-interacting region, residues approximately 150-350 (the "interactive core"), overlapped portions of the M- and C-domains and included a putative hydrophobic-rich interdomain segment which may be a preferential site of interaction with TRiC. This segment may also be important for microtubule assembly and/or tubulin dimer formation. Removal of two residues from the N-terminal end or ca. 27 residues from the C-terminal and caused the polypeptide to arrest on TRiC. It is proposed that N- and C-terminal regions of beta-tubulin structurally interact with TRiC-binding region approximately 150-350 to inhibit binding to TRiC.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for American Chemical Society
Loading ...
Support Center