Structural basis for α-tubulin-specific and modification state-dependent glutamylation

• Published in: Nature chemical biology Vol. 20; no. 11; pp. 1493 - 1504
• Main Authors: Mahalingan, Kishore K., Grotjahn, Danielle A., Li, Yan, Lander, Gabriel C., Zehr, Elena A., Roll-Mecak, Antonina
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01-11-2024; Nature Publishing Group
• Subjects: 631/535; 631/57/2265; 631/92/458; 631/92/607; Biochemical Engineering; Biochemistry; Bioorganic Chemistry; Cell Biology; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Complexity; Crosstalk; Cryoelectron Microscopy; Dimers; Electron microscopy; Feedback; Feedback loops; Humans; Kinetics; Microscopy; Microtubules; Microtubules - metabolism; Models, Molecular; Pattern generation; Pattern recognition; Peptide Synthases - chemistry; Peptide Synthases - metabolism; Positive feedback; Protein Processing, Post-Translational; Tails; Transmission electron microscopy; Tubulin; Tubulin - chemistry; Tubulin - metabolism; Tyrosine
• ISSN: 1552-4450; 1552-4469; 1552-4469
• DOI: 10.1038/s41589-024-01599-0

Microtubules have spatiotemporally complex posttranslational modification patterns. Tubulin tyrosine ligase-like (TTLL) enzymes introduce the most prevalent modifications on α-tubulin and β-tubulin. How TTLLs specialize for specific substrate recognition and ultimately modification-pattern generation is largely unknown. TTLL6, a glutamylase implicated in ciliopathies, preferentially modifies tubulin α-tails in microtubules. Cryo-electron microscopy, kinetic analysis and single-molecule biochemistry reveal an unprecedented quadrivalent recognition that ensures simultaneous readout of microtubule geometry and posttranslational modification status. By binding to a β-tubulin subunit, TTLL6 modifies the α-tail of the longitudinally adjacent tubulin dimer. Spanning two tubulin dimers along and across protofilaments (PFs) ensures fidelity of recognition of both the α-tail and the microtubule. Moreover, TTLL6 reads out and is stimulated by glutamylation of the β-tail of the laterally adjacent tubulin dimer, mediating crosstalk between α-tail and β-tail. This positive feedback loop can generate localized microtubule glutamylation patterns. Our work uncovers general principles that generate tubulin chemical and topographic complexity.
Cryo-electron microscopy (cryo-EM), kinetic analysis and single-molecule biochemistry reveal how the tubulin tyrosine ligase-like 6 (TTLL6) glutamylase binds reads microtubule geometry and modification state of neighboring tubulins, enabling a spatial positive feedback loop for microtubule modification.