Acetylation of lysine 40 in alpha-tubulin is not essential in Tetrahymena thermophila.
In Tetrahymena, at least 17 distinct microtubule structures are assembled from a single primary sequence type of alpha- and beta-tubulin heterodimer, precluding distinctions among microtubular systems based on tubulin primary sequence isotypes. Tetrahymena tubulins also are modified by several types of posttranslational reactions including acetylation of alpha-tubulin at lysine 40, a modification found in most eukaryotes. In Tetrahymena, axonemal alpha-tubulin and numerous other microtubules are acetylated. We completely replaced the single type of alpha-tubulin gene in the macronucleus with a version encoding arginine instead of lysine 40 and therefore cannot be acetylated at this position. No acetylated tubulin was detectable in these transformants using a monoclonal antibody specific for acetylated lysine 40. Surprisingly, mutants lacking detectable acetylated tubulin are indistinguishable from wild-type cells. Thus, acetylation of alpha-tubulin at lysine 40 is non-essential in Tetrahymena. In addition, isoelectric focusing gel analysis of axonemal tubulin from cells unable to acetylate alpha-tubulin leads us to conclude that: (a) most or all ciliary alpha-tubulin is acetylated, (b) other lysines cannot be acetylated to compensate for loss of acetylation at lysine 40, and (c) acetylated alpha-tubulin molecules in wild-type cells contain one or more additional charge-altering modifications.
Gaertig
J
J
Department of Biology, University of Rochester, New York 14627, USA.
Cruz
M A
MA
Bowen
J
J
Gu
L
L
Pennock
D G
DG
Gorovsky
M A
MA
D000107:Acetylation; D000818:Animals; D018014:Gene Transfer Techniques; D008239:Lysine / Q000737:chemistry; D008870:Microtubules / Q000502:physiology; D009154:Mutation; D011499:Protein Processing, Post-Translational; D013768:Tetrahymena / Q000378:metabolism*; D014404:Tubulin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D014404:Tubulin; D008239:Lysine