Fig. 6. Sequence alignment of -tubulin isoforms. The C-terminal portion of 11 human -tubulin isoforms is shown (full-length sequences are available in Fig. S1 in supplementary material). Amino acid identity is indicated with black highlighting, with the exception of the grB cleavage site, which is highlighted in grey; mutation of this site (indicated by an arrow) was found to ablate grB cleavage in vitro. The -tubulin isoforms include those previously described in the literature, together with additional proteins annotated in the ENSEMBL Genome Browser (www.ensembl.org; protein family ENSF00000000220) that could be independently verified as expressed sequence tags through the NCBI Blast server (www.ncbi.nlm.nih.gov/BLAST). Alignments were generated using ClustalW and the length of each isoform is indicated in brackets.