Characterization of a major brain tubulin variant which cannot be tyrosinated

Abstract

Brain tubulin preparations contain an abundant type of tubulin which does not undergo the normal cycle of tyrosination-detyrosination, and whose nature is still unknown. We have used peptide sequence analysis and mass spectrometry combined with immunological procedures to show that this non-tyrosinatable tubulin has a specific primary structure. It differs from the tyrosinated isotype in that it lacks a carboxy-terminal glutamyl-tyrosine group on its alpha-subunit. Thus, non-tyrosinatable tubulin originates from a well-defined posttranslational modification of the tubulin primary structure which is located at the expected site of activity of tubulin tyrosine ligase. This probably accounts for the reason why it cannot be tyrosinated. The significance of this abundant brain isotubulin and the metabolic pathway involved in its formation remain to be elucidated. This should shed light on the relation between the structural diversity of the carboxy terminus of alpha-tubulin and the regulation of functional properties of microtubules.

Polyglycylation of tubulin in the diplomonad Giardia lamblia, one of the oldest eukaryotes

“…Two other unique post-translational modifications involve the presence of a polyglutamyl-or polyglycyl side chain attached via an isopeptide bond to a particular glutamic acid residue in the carboxyterminal region of ct-and 13-tubulin. The exact position of this modified residue has been identified in all brain tubulins [3,8,[10][11][12][13]. The more recently discovered polyglycylation has been documented for ct-and 13-tubulin from the ciliary axonemal microtubules of the protist Paramecium [14] and from the sperm axonemal microtubules of mammals [15] (Plessmann, U. and Weber, K. unpublished results) and sea urchins [16].…”

“…Thus the carboxyterminal tyrosine of certain ct-tubulins is subject to a detyrosination/tyrosination cycle based on a carboxypeptidase and the well-characterized tubulin-tyrosine ligase [5,6]. After loss of the tyrosine and penultimate glutamic acid residue the resulting tubulin is no longer a substrate for tubulintyrosine ligase [7][8][9]. Two other unique post-translational modifications involve the presence of a polyglutamyl-or polyglycyl side chain attached via an isopeptide bond to a particular glutamic acid residue in the carboxyterminal region of ct-and 13-tubulin.…”

Low expression of human tubulin tyrosine ligase and suppressed tubulin tyrosination/detyrosination cycle are associated with impaired neuronal differentiation in neuroblastomas with poor prognosis

“…16,18,28 The PVDF membranes spotted with equal amount (1 g) of synthetic peptides corresponding to COOH terminal 7 amino acid residues of Tyr-tubulin (CEEE-GEEY), Glu-tubulin (CGEEEGEE) and ⌬2-tubulin (CEGEEEGE) were immunoblotted with rabbit anti-Tyr-tubulin antibody (Fig. 3a, top), anti-Glu-tubulin antibody (Fig.…”

“…14 Recently, rat TTL cDNA has also been isolated. 15 Interestingly, in 1991, Paturle-Lafanechere et al 16 identified a nontyrosinatable variant of tubulin that lacked 2 amino acid residues, glutamic acid and tyrosine, at the COOH terminus (⌬2-tubulin). ⌬2-tubulin was found to accumulate in mature neurons and in stable microtubule assemblies in cells.…”

Cytosolic Carboxypeptidase 1 Is Involved in Processing α- and β-Tubulin

“…The deTyr-tubulin can be converted back to Tyr-tubulin through the addition of Tyr by the enzyme tubulin tyrosine ligase (TTL) (22). Alternatively, the deTyr-tubulin can be converted to delta2-tubulin by the removal of C-terminal Glu (18,23). Another post-translational modification of ␣-tubulin as well as ␤-tubulin involves the addition and removal of polyglutamyl (polyE) side chains (18,24).…”