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The high degree of tubulin heterogeneity in neurons is controlled mainly at the posttranslational level. Several variants of alpha-tubulin can be posttranslationally labeled after incubation of cells with 3Hacetate or 3Hglutamate. Peptides carrying the radioactive moiety were purified by high-performance liquid chromatography. Amino acid analysis, Edman degradation sequencing, and mass spectrometric analysis of these peptides led to the characterization of a posttranslational modification consisting of the successive addition of glutamyl units on the gamma-carboxyl group of a glutamate residue (Glu445). This modification, localized within a region of alpha-tubulin that is important in the interactions of tubulin with microtubule-associated proteins and calcium, could play a role in regulating microtubule dynamics.
Eddé et al. (Fri,) studied this question.