GO:0070740 tubulin-glutamic acid ligase activity

GO:0070740, tubulin-glutamic acid ligase activity, is a Gene Ontology molecular_function term that captures the enzymatic addition of glutamate residues to tubulin. This posttranslational modification, known as tubulin glutamylation, occurs on the gamma-carboxyl group of specific glutamate residues within the tubulin molecule and is a key component of the tubulin code. Researchers study this activity because it directly modulates microtubule stability, motor protein recruitment, and cellular processes such as mitosis, neuronal transport, and ciliary beating. The reaction is catalyzed by enzymes that belong to the tubulin tyrosine ligase-like (TTLL) family and related ligases, which transfer glutamate from a donor substrate to tubulin. Because the modification is reversible and tightly regulated, its dysregulation has been implicated in a range of human diseases, including cancer and neurodegeneration. Understanding GO:0070740 therefore requires both biochemical characterization of the ligase enzymes and functional studies in relevant cell and animal models.

In simple terms, GO:0070740 describes the activity of an enzyme that attaches one or more glutamate molecules to a tubulin protein. According to the QuickGO definition, this activity catalyzes the posttranslational transfer of one or more glutamate residues to the gamma-carboxyl group(s) of one or more specific glutamate residues on a tubulin molecule. This is a ligase activity because it forms a new covalent bond between the glutamate donor and the tubulin acceptor, and it is specific to tubulin substrates rather than general protein glutamylation. The term is classified under molecular_function and is synonymous with tubulin-glutamate ligase activity and tubulin glutamylase activity.

GO:0070740 is important because tubulin glutamylation is a major regulatory modification of the microtubule cytoskeleton. By adding glutamate residues to tubulin, this activity alters the surface chemistry of microtubules and controls how they interact with molecular motors, severing enzymes, and microtubule-associated proteins. This regulation is essential for proper cell division, intracellular transport, and ciliary function, and its disruption has been associated with cancer, neurodegeneration, and developmental disorders in published studies. Consequently, researchers targeting GO:0070740-related enzymes seek to understand both the basic biology of microtubule regulation and the therapeutic potential of modulating this activity.

The following genes and proteins are experimentally linked to tubulin glutamylation and GO:0070740-related activity.

Tubulin glutamylation is regulated by the opposing activities of glutamylases and deglutamylases, and by the availability of glutamate donors. The modification is also influenced by the expression levels of TTLL family enzymes, which can be transcriptionally and posttranslationally controlled. In addition, the tubulin code itself can feedback on ligase recruitment, and crosstalk with other tubulin modifications such as detyrosination and acetylation modulates the final pattern. Researchers studying GO:0070740 often examine how these regulatory layers change in disease states and in response to cellular stress.

Altered tubulin glutamylation has been observed in cancer cells and can affect mitotic spindle assembly, cell division, and sensitivity to microtubule-targeting drugs. Enzymes with GO:0070740 activity are therefore studied as potential modifiers of chemoresistance and tumor progression.

In neurons, proper tubulin glutamylation is required for axonal transport and synaptic function, and its imbalance has been linked to neurodegenerative phenotypes in published models. Mutations affecting glutamylases or deglutamylases can lead to neuronal dysfunction.

Cilia and flagella depend on a precise tubulin code, and defects in glutamylation enzymes have been associated with ciliary dysfunction and retinal degeneration. This makes GO:0070740-related genes candidates for ciliopathy research.

In vitro assays using recombinant enzymes and tubulin substrates can directly measure glutamate transfer and are foundational for confirming GO:0070740 activity. These assays often use radiolabeled or fluorescent glutamate to track modification.

Mass spectrometry can map the exact sites of glutamylation on tubulin and quantify changes across conditions, providing high-resolution readouts of the tubulin code. Proteomic approaches also identify interaction partners of glutamylases.

Specific antibodies against polyglutamylated tubulin allow visualization and quantification of the modification by immunofluorescence and immunoblotting. These tools are widely used to study glutamylation in cells and tissues.

CRISPR screens combined with imaging or sequencing can identify genes that regulate glutamylation and its downstream effects. Live-cell imaging of microtubules and motors reveals how the modification affects dynamics.

Researchers studying tubulin-glutamic acid ligase activity-related genes often need to determine whether a candidate gene is causally involved in microtubule regulation, ciliary function, or disease phenotypes. EDITGENE provides validated CRISPR cell models and screening services to accelerate this work.

GO:0070740, tubulin-glutamic acid ligase activity, is a central enzymatic activity in the tubulin code that controls microtubule behavior and cellular processes ranging from mitosis to ciliary function. Its dysregulation is associated with cancer, neurodegeneration, and ciliopathies, making it a compelling target for basic and translational research. By combining biochemical assays, advanced imaging, and CRISPR-based models, researchers can dissect the precise roles of glutamylases and their therapeutic potential.