A) Representation of the differential glutamylation of α- and β-tubulin, and which epitopes can be detected by the glutamylation-specific antibodies used in this study. The most prominent tubulin isotypes in brain, α1- and β2-tubulin are shown with their C-terminal tails represented as amino-acid sequences. The main modification sites, glutamates (E) 445 on α1-tubulin (Eddé et al, 1990) and E435 on β2-tubulin (Rüdiger et al, 1992) are indicated. However, all glutamate residues in these C-terminal tails (light grey circles) could potentially be glutamylated. Glutamylation generated by TTLL1 is colour-coded red, while TTLL7-catalysed glutamylation is orange. Note that under wild-type conditions, TTLL1 and TTLL7 exclusively modify α- and β-tubulin, respectively in brain tissue. 