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TUBB4B

Domain

The highly acidic C-terminal region may bind cations such as calcium.

The MREI motif is common among all beta-tubulin isoforms and may be critical for tubulin autoregulation.

Function

Tubulin is the major constituent of microtubules, a cylinder consisting of laterally associated linear protofilaments composed of alpha- and beta-tubulin heterodimers. Microtubules grow by the addition of GTP-tubulin dimers to the microtubule end, where a stabilizing cap forms. Below the cap, tubulin dimers are in GDP-bound state, owing to GTPase activity of alpha-tubulin.

Involvement in disease

Leber congenital amaurosis with early-onset deafness

LCAEOD

An autosomal dominant disease characterized by severe retinal degeneration and sensorineural hearing loss. Symptoms occur within the first decade of life. Onset at birth is observed in some patients.

None

The disease is caused by variants affecting the gene represented in this entry.

Post-translational modifications

Some glutamate residues at the C-terminus are polyglutamylated, resulting in polyglutamate chains on the gamma-carboxyl group (PubMed:26875866). Polyglutamylation plays a key role in microtubule severing by spastin (SPAST). SPAST preferentially recognizes and acts on microtubules decorated with short polyglutamate tails: severing activity by SPAST increases as the number of glutamates per tubulin rises from one to eight, but decreases beyond this glutamylation threshold (PubMed:26875866). Glutamylation is also involved in cilia motility (By similarity).

Some glutamate residues at the C-terminus are monoglycylated but not polyglycylated due to the absence of functional TTLL10 in human. Monoglycylation is mainly limited to tubulin incorporated into cilia and flagella axonemes, which is required for their stability and maintenance. Flagella glycylation controls sperm motility. Both polyglutamylation and monoglycylation can coexist on the same protein on adjacent residues, and lowering glycylation levels increases polyglutamylation, and reciprocally.

Phosphorylated on Ser-172 by CDK1 during the cell cycle, from metaphase to telophase, but not in interphase. This phosphorylation inhibits tubulin incorporation into microtubules.

Sequence Similarities

Belongs to the tubulin family.

Tissue Specificity

Ubiquitous.

Cellular localization

Alternative names

TUBB2C, TUBB4B, Tubulin beta-4B chain, Tubulin beta-2 chain, Tubulin beta-2C chain

swissprot:P68371 entrezGene:7280 omim:602660 swissprot:Q13885 entrezGene:347733 swissprot:Q9BVA1 entrezGene:10383