TTLL4
Domain
The flexible c-MTBD (cationic microtubule binding domain) region mediates binding to microtubules. It is positively charged and becomes ordered when bound to microtubules: it interacts with a negatively charged patch on tubulin. The presence of positive charges in the c-MTBD region is essential for proper binding.
Arg-727 is the main determinant for regioselectivity, which segregates between initiases and elongases in all tubulin--tyrosine ligase family. A glutamine residue at this position is found in elongases TTLL6, TTLL9, TTLL11, TTLL13, TTLL10 and favors glutamate-chain elongation, whereas an arginine residue is found in initiases TTLL2, TTLL4, TTLL5, TTLL3, TTLL8 and favors initiation.
Function
Monoglutamylase which modifies both tubulin and non-tubulin proteins, adding a single glutamate on the gamma-carboxyl group of specific glutamate residues of target proteins. Involved in the side-chain initiation step of the polyglutamylation reaction but not in the elongation step. Preferentially modifies beta-tail tubulin over the alpha-tubulin. Monoglutamylates nucleosome assembly proteins NAP1L1 and NAP1L4. Monoglutamylates nucleotidyltransferase CGAS, leading to inhibition of CGAS catalytic activity, thereby preventing antiviral defense function. Involved in KLF4 glutamylation which impedes its ubiquitination, thereby leading to somatic cell reprogramming, pluripotency maintenance and embryogenesis.
Sequence Similarities
Belongs to the tubulin--tyrosine ligase family.
Cellular localization
- Cytoplasm
- Cell projection
- Cilium
- Cytoplasm
- Cytoskeleton
- Cilium basal body
- Located in cilia. In some cells, also found in basal bodies.
Alternative names
KIAA0173, TTLL4, Tubulin monoglutamylase TTLL4, Protein monoglutamylase TTLL4, Tubulin--tyrosine ligase-like protein 4