Beta tubulin of bull sperm is polyglycylated.

Carboxy-terminal fragments of alpha and beta tubulin from bull sperm were isolated and characterized by automated sequencing and mass spectrometry. About 60% of sperm alpha tubulin is polyglycylated. The lateral chain, which can reach 13 residues in length, is covalently attached via an isopeptide bond. The fully detyrosinated sperm alpha tubulin lacks polyglycylation. Thus mammalian sperm microtubules differ from the ciliary axonemal microtubules of the protozoan Paramecium for which others have documented a complete polyglycylation of both alpha and beta tubulin.