β tubulin of bull sperm is polyglycylated

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