The primary structure of tubulin. Sequences of the carboxyl terminus and seven other cyanogen bromide peptides from the alpha-chain.

The alpha-chain of calf brain tubulin was fragmented by treatment with cyanogen bromide and eight peptides together accounting for 108 residues were purified and sequenced. The COOH-terminal peptide contains a fractional amount (about 0.3 residues) of tyrosine at its COOH-terminus; this presumably represents tyrosine that is added post-translationally to alpha-tubulin. The beta-chain can be phosphorylated, and the probable site of this modification is identified also in the COOH-terminal peptide. Comparison of the sequences described here with the sequence of actin reveals no homology between actin and tubulin.