Effects of tubulin acetylation and tubulin acetyltransferase binding on microtubule structure.
Tubulin undergoes posttranslational modifications proposed to specify microtubule subpopulations for particular functions. Most of these modifications occur on the C-termini of tubulin and may directly affect the binding of microtubule-associated proteins (MAPs) or motors. Acetylation of Lys-40 on α-tubulin is unique in that it is located on the luminal surface of microtubules, away from the interaction sites of most MAPs and motors. We investigate whether acetylation alters the architecture of microtubules or the conformation of tubulin, using cryo-electron microscopy (cryo-EM). No significant changes are observed based on protofilament distributions or microtubule helical lattice parameters. Furthermore, no clear differences in tubulin structure are detected between cryo-EM reconstructions of maximally deacetylated or acetylated microtubules. Our results indicate that the effect of acetylation must be highly localized and affect interaction with proteins that bind directly to the lumen of the microtubule. We also investigate the interaction of the tubulin acetyltransferase, αTAT1, with microtubules and find that αTAT1 is able to interact with the outside of the microtubule, at least partly through the tubulin C-termini. Binding to the outside surface of the microtubule could facilitate access of αTAT1 to its luminal site of action if microtubules undergo lateral opening between protofilaments.
Biophysics Graduate Group, University of California, Berkeley, Berkeley, CA 94720 Howard Hughes Medical Institute at the Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720 Department of Molecular and Cellular Physiology, Stanford School of Medicine, Stanford, CA 94305 Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720.
Stuart C
SC
Howes
Gregory M
GM
Alushin
Toshinobu
T
Shida
Maxence V
MV
Nachury
Eva
E
Nogales
D000107:Acetylation; D000123:Acetyltransferases / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D020285:Cryoelectron Microscopy; D004926:Escherichia coli; D016547:Kinesins / Q000737:chemistry / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000378:metabolism*; D008870:Microtubules / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D011499:Protein Processing, Post-Translational; D013552:Swine; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism*
D008869:Microtubule-Associated Proteins; D014404:Tubulin; D000123:Acetyltransferases; D016547:Kinesins