biostudies-literatureUnknown11(34)Campbell JMicrotubules (MTs) undergo diverse posttranslational modifications that regulate their structural and functional properties. Among these, polyglutamylation-a dominant and conserved modification targeting unstructured tubulin C-terminal tails-plays a pivotal role in defining the tubulin code. Here, we describe a mechanism by which tubulin tyrosine ligase-like 11 (TTLL11) expands and diversifies the code. Cryo-electron microscopy revealed a unique bipartite MT recognition strategy wherein TTLL11 binding and catalytic domains engage adjacent MT protofilaments. Biochemical and cellular assays identified previously uncharacterized polyglutamylation patterns, showing that TTLL11 directly extends the primary polypeptide chains of α- and β-tubulin in vitro, challenging the prevailing paradigms empScience advanceseadw1561https://www.ebi.ac.uk/biostudies/studies/S-EPMC12366701biostudies-literatureMechanistic insights into TTLL11 polyglutamylase-mediated primary tubulin chain elongation.PMC12366701Snajdr IBasta MGutsche IVosahlikova MMotlova LNovakova ZMoutin MJVolnikova MDesfosses ACampbell JUstinova KKudlacova JBarinka CIsmail SfalseMechanistic insights into TTLL11 polyglutamylase-mediated primary tubulin chain elongation.Microtubules (MTs) undergo diverse posttranslational modifications that regulate their structural and functional properties. Among these, polyglutamylation-a dominant and conserved modification targeting unstructured tubulin C-terminal tails-plays a pivotal role in defining the tubulin code. Here, we describe a mechanism by which tubulin tyrosine ligase-like 11 (TTLL11) expands and diversifies the code. Cryo-electron microscopy revealed a unique bipartite MT recognition strategy wherein TTLL11 binding and catalytic domains engage adjacent MT protofilaments. Biochemical and cellular assays identified previously uncharacterized polyglutamylation patterns, showing that TTLL11 directly extends the primary polypeptide chains of α- and β-tubulin in vitro, challenging the prevailing paradigms emp2025-01-01T00:00:00Z2025 Aug2026-05-29T15:04:11.748Z2026-04-08T05:11:35.159ZS-EPMC123667014083409610.1126/sciadv.adw1561