Ncubating purified bovine brain tubulin with recombinant HisSIRT2 in the presence of 1 mM NAD (b-Nicotinamide adenine dinucleotide, Sigma N8285) for 2 h at 37uC with constant mixing. The resulting modified tubulins were cycled through one round of polymerization/depolymerization to remove the enzyme (verified by SDS-PAGE, data not shown) before flash-freezing in liquid nitrogen and storage at 280uC. Untreated, acetylated or deacetylated tubulins were polymerized for 20 min 
at 37uC in BRB80 at a concentration of 10 mg/ml in the presence of 20 DMSO (v/v), 2 mM GTP, 20 mM taxol, 0.5 mM PMSF and 4 mM MgCl2.Immunostaining of acetylated and deacetylated microtubulesPolymerized microtubules were adsorbed onto coverslips and stained with 6-11B-1 antibodies without fixation (live) or after fixation with 4 paraformaldehyde (PFA fixed) in PBS containingCryo-EM Localization of Acetyl-K40 on Microtubules20 mM taxol. All subsequent steps were carried out in BRB80+20 mM taxol. The cover slips were blocked with 5 mg/ ml casein for 30 min, incubated with primary antibodies for 1 h, washed three times, incubated with secondary antibodies for 1 h, washed three times, and mounted with Prolong Gold. The images were obtained on an inverted epi-fluorescence microscope Nikon TE2000E, equipped with 60X 1.40 NA objective and a Photometrics CoolSnap HQ camera.Supporting InformationFigure S1 Purification of recombinant MEC-17 and SIRT2 enzymes and Fab fragment preparation. A,B) Coomassie-stained SDS-PAGE gels showing purification profile of recombinant A) GST-MEC-17 or B) His-SIRT2. C) Coomassiestained SDS-PAGE gel showing preparation of Fab fragments from the monoclonal 6-11B-1 antibody. (TIF) Figure S2 Raw cryo-EM images of representativemicrotubule segments. Filament sections have been excised from larger micrographs and enlarged to show detail. Shown are order Fruquintinib representative sections of A) control (no enzyme treatment, no Fab binding), B) MEC-17-acetylated and 6-11B-1 Fab-decorated, and C) SIRT2-deactylated and 6-11B-1 Fab-decorated microtubules. Scale bar, 25 nm. (TIF)Figure SRepresentative power spectra. A) A representative power spectrum from a single vitrified control microtubule. B) A representative power spectrum from a single vitrified MEC-17acetylated microtubule decorated with 6-11B-1 Fab. Regular Fab decoration is indicated by the presence of a 1/8 nm layer line, compared to the control microtubule (A). C) A representative power spectrum from a single vitrified SIRT2-deacetylated microtubule decorated with 6-11B-1 Fab. A weaker 1/8 nm signal is observed, corresponding to lower Fab occupancy. (TIF)Figure S4 Monoclonal 6-11B-1 and polyclonal antiacetyl-K40 antibodies recognize acetylated but not unacetylated microtubules in cells. A) COS7 and PtK2 cells were fixed and double stained with monoclonal 6-11B-1 and total tubulin antibodies (left SPDB panels) or polyclonal anti-acetyl-K40 and total tubulin antibodies (right panels). Neither antibody recognizes microtubule filaments in PtK2 cells which contain only unacetylated (never modified) a-tubulin. B) COS7 16574785 and PtK2 cells expressing the acetytransferase mCit-MEC-17 (green) were double stained with monoclonal 6-11B-1 (red) and total tubulin (magenta) antibodies (left panels) or with polyclonal anti-acetyl-K40 (red) and total tubulin (magenta) antibodies (right panels). Both antibodies recognize the highly acetylated microtubules induced by expression of mCit-MEC-17. Scale bars, 20 mm. (TIF) Figure S5 The 6-11B-1.Ncubating purified 
bovine brain tubulin with recombinant HisSIRT2 in the presence of 1 mM NAD (b-Nicotinamide adenine dinucleotide, Sigma N8285) for 2 h at 37uC with constant mixing. The resulting modified tubulins were cycled through one round of polymerization/depolymerization to remove the enzyme (verified by SDS-PAGE, data not shown) before flash-freezing in liquid nitrogen and storage at 280uC. Untreated, acetylated or deacetylated tubulins were polymerized for 20 min at 37uC in BRB80 at a concentration of 10 mg/ml in the presence of 20 DMSO (v/v), 2 mM GTP, 20 mM taxol, 0.5 mM PMSF and 4 mM MgCl2.Immunostaining of acetylated and deacetylated microtubulesPolymerized microtubules were adsorbed onto coverslips and stained with 6-11B-1 antibodies without fixation (live) or after fixation with 4 paraformaldehyde (PFA fixed) in PBS containingCryo-EM Localization of Acetyl-K40 on Microtubules20 mM taxol. All subsequent steps were carried out in BRB80+20 mM taxol. The cover slips were blocked with 5 mg/ ml casein for 30 min, incubated with primary antibodies for 1 h, washed three times, incubated with secondary antibodies for 1 h, washed three times, and mounted with Prolong Gold. The images were obtained on an inverted epi-fluorescence microscope Nikon TE2000E, equipped with 60X 1.40 NA objective and a Photometrics CoolSnap HQ camera.Supporting InformationFigure S1 Purification of recombinant MEC-17 and SIRT2 enzymes and Fab fragment preparation. A,B) Coomassie-stained SDS-PAGE gels showing purification profile of recombinant A) GST-MEC-17 or B) His-SIRT2. C) Coomassiestained SDS-PAGE gel showing preparation of Fab fragments from the monoclonal 6-11B-1 antibody. (TIF) Figure S2 Raw cryo-EM images of representativemicrotubule segments. Filament sections have been excised from larger micrographs and enlarged to show detail. Shown are representative sections of A) control (no enzyme treatment, no Fab binding), B) MEC-17-acetylated and 6-11B-1 Fab-decorated, and C) SIRT2-deactylated and 6-11B-1 Fab-decorated microtubules. Scale bar, 25 nm. (TIF)Figure SRepresentative power spectra. A) A representative power spectrum from a single vitrified control microtubule. B) A representative power spectrum from a single vitrified MEC-17acetylated microtubule decorated with 6-11B-1 Fab. Regular Fab decoration is indicated by the presence of a 1/8 nm layer line, compared to the control microtubule (A). C) A representative power spectrum from a single vitrified SIRT2-deacetylated microtubule decorated with 6-11B-1 Fab. A weaker 1/8 nm signal is observed, corresponding to lower Fab occupancy. (TIF)Figure S4 Monoclonal 6-11B-1 and polyclonal antiacetyl-K40 antibodies recognize acetylated but not unacetylated microtubules in cells. A) COS7 and PtK2 cells were fixed and double stained with monoclonal 6-11B-1 and total tubulin antibodies (left panels) or polyclonal anti-acetyl-K40 and total tubulin antibodies (right panels). Neither antibody recognizes microtubule filaments in PtK2 cells which contain only unacetylated (never modified) a-tubulin. B) COS7 16574785 and PtK2 cells expressing the acetytransferase mCit-MEC-17 (green) were double stained with monoclonal 6-11B-1 (red) and total tubulin (magenta) antibodies (left panels) or with polyclonal anti-acetyl-K40 (red) and total tubulin (magenta) antibodies (right panels). Both antibodies recognize the highly acetylated microtubules induced by expression of mCit-MEC-17. Scale bars, 20 mm. (TIF) Figure S5 The 6-11B-1.
