Taurine is an unexpected PTM for tubulin or any other protein, and this is, to our knowledge, the first report of taurine incorporation into a large protein. Taurine is almost always found as a free amino acid or in small peptides, such as g-glutamyltaurine . The only macromolecular occurrence of taurine previously reported is as a functional, clinically significant posttranscriptional modification of mitochondrial tRNA . The exact role of taurine as a free amino acid is controversial although it is clear that it is among the most abundant free amino acids. As a free amino acid, it accounts for about 0.1% of total adult human dry weight . Taurine deficiency is associated with several diseases, whose nature and severity can vary depending on age, among other things .