A combination of posttranslational modifications is responsible for the production of neuronal alpha-tubulin heterogeneity.
We describe the presence of alpha-tubulin and MAP2 acetyltransferase activities in mouse brain. The enzyme(s) copurified with microtubules through two cycles of assembly-disassembly. Incubation of microtubule proteins with [3H]acetyl CoA resulted in a strong labeling of both alpha-tubulin and MAP2. To determine the site of the modification, tubulin was purified and digested with Glu-C endoproteinase. A unique radioactive peptide was detected and purified by HPLC. Edman degradation sequencing showed that this peptide contained epsilon N-acetyllysine at position 40 of the alpha-tubulin molecule. This result demonstrates that mouse brain alpha-tubulin was acetylated at the same site as in Chlamydomonas. Isoelectric focusing analysis showed that acetylated alpha-tubulin was resolved into five isoelectric variants, denoted alpha 3 and alpha 5 to alpha 8. This heterogeneity is not due to acetylation of other sites but results from a single acetylation of Lys40 of an heterogeneous population of alpha-tubulin isoforms. These isoforms are produced by posttranslational addition of one to five glutamyl units. Thus, neuronal alpha-tubulin is extensively modified by a combination of modifications including acetylation, glutamylation, tyrosylation, and other yet unknown modifications.
Laboratoire de Biochimie Cellulaire, Collège de France, Paris.
B
B
Eddé
J
J
Rossier
J P
JP
Le Caer
Y
Y
Berwald-Netter
A
A
Koulakoff
F
F
Gros
P
P
Denoulet
D000107:Acetylation; D000123:Acetyltransferases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001253:Astrocytes / Q000737:chemistry / Q000378:metabolism*; D001921:Brain / Q000201:enzymology; D001923:Brain Chemistry; D002478:Cells, Cultured; D002696:Chlamydomonas / Q000201:enzymology / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D005971:Glutamates / Q000378:metabolism; D018698:Glutamic Acid; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000032:analysis / Q000378:metabolism*; D008969:Molecular Sequence Data; D009474:Neurons / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D014404:Tubulin / Q000032:analysis / Q000378:metabolism*
D005971:Glutamates; D008869:Microtubule-Associated Proteins; D014404:Tubulin; D018698:Glutamic Acid; D000123:Acetyltransferases; C071107:microtubule-associated protein acetyltransferase; C049182:alpha-tubulin acetylase