Journal: Science Advances
Article Title: Mechanistic insights into TTLL11 polyglutamylase–mediated primary tubulin chain elongation
doi: 10.1126/sciadv.adw1561
Figure Lengend Snippet: ( A ) TTLL11 binding to pMTs analyzed using TIRF microscopy. The TTLL11 representation shows the catalytic domain (purple), MT-BHB (pink), and site-specific mutations (described in fig. S6). MTs were attached to coverslips and incubated with 100 nM Janelia Fluor 549–labeled TTLL11 variants (red). Scale bars, 2 μm. ( B ) Quantification of TIRF images for full-length (FL) TTLL11, the N-terminally truncated variant (122 to 710), the catalytically inactive E441G, and the KKKR-EEEE mutant show binding with similar intensity. Deleting the MT-BHB or catalytic domains abolishes TTLL11 binding. Mutations in TTLL11 helix α 11 (R601E and I594W) reduced binding by 60 and 80%, respectively. Norm., normalized. ( C to E ) Tubulin C-tails are critical for TTLL11 interactions. (C) CBB-stained gel of truncated MTs. AspN truncates the β-tubulin, and subtilisin truncates both α- and β-tubulin C-tails. TIRF microscopy images (D) and quantification (E) show that AspN-treated MTs exhibit ~50% reduction in TTLL11 binding, while the complete loss of binding is observed for subtilisin-treated MTs. Data are shown as mean fluorescent intensity from n = 2 replicates with 114, 93, and 58 MTs quantified in each sample. Statistical significance: Unpaired t test with Welch correction; **** P < 0.0001. The black bar: Median value with 95% confidence interval. Scale bars, 5 μm. Ctrl, control. Created in BioRender. Barinka, C. (2025) https://BioRender.com/sr4q7do . ( F ) In vitro polyglutamylation of MTs from HEK293T cells by TTLL11 variants, analyzed by WB, confirms activity for FL and 122 to 710. Variants lacking the MT-BHB domain show no activity. I594W and R601E mutants show reduced activity. ( G ) Assay in HEK293T cells transfected with TTLL11 variants shows polyglutamylation consistent with in vitro findings. TTLL6 and TTLL7 show specificity for α- and β-tubulin, respectively. An unidentified TTLL11 substrate, represented by a polyE-stained band in between α- and β-tubulin (between red lines), is glutamylated regardless of the MT-BHB mutations. Only TTLL7 shows a signal of the GT335 antibody specific for branching.
Article Snippet: Membranes were incubated with primary antibodies, with secondary fluorescent antibodies (antimouse conjugated to Alexa Fluor 488 and anti–guinea pig, antirabbit, and antirat conjugated to cyanine-3, all used at 1:2000) and last revealed with ChemiDoc camera (Bio-Rad Laboratories).
Techniques: Binding Assay, Microscopy, Incubation, Labeling, Variant Assay, Mutagenesis, Staining, Control, In Vitro, Activity Assay, Transfection