Protein identification was performed on an in-solution tryptic digest of a MAP-rich tubulin sample with Proteome Discoverer v 2.4 (Thermo Scientific, Waltham MA) using a Sequest HT search engine. MS/MS data were searched against an NCBI, Sus scrofa protein database (downloaded June 2020). The search was set-up for full tryptic peptides with a maximum of two missed cleavage sites. Oxidized methionine was included as a variable modification. Carbamidomethylation of cysteine was set as a fixed modification. The precursor mass tolerance threshold was set at 10 ppm with a fragment tolerance of 0.02 Da. The significance threshold of the ion score was calculated based on a false discovery rate of ≤ 1% using Protein FDR Validator with Posterior Error Probabilities provided by the Percolator algorithm associated with the Sequest HT search engine.