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tubulin, alpha 1 (testis specific)
Identifiers
Symbol	TUBA1
Entrez	7277
HUGO	12407
OMIM	191110
RefSeq	NM_006000
UniProt	P68366
Other data
Locus	Chr. 2 q36.1

tubulin, alpha 2
Identifiers
Symbol	TUBA2
Entrez	7278
HUGO	12408
OMIM	602528
RefSeq	NM_006001
UniProt	Q13748
Other data
Locus	Chr. 13 q11

tubulin, beta
Identifiers
Symbol	TUBB
Entrez	203068
HUGO	20778
OMIM	191130
RefSeq	NM_178014
UniProt	P07437
Other data
Locus	Chr. 6 p21.33

A Tubulin is one of several members of a small family of globular proteins. The most common members of the tubulin family are α-tubulin and β-tubulin, the proteins that make up microtubules. Each has a molecular weight of approximately 55 kiloDaltons. Microtubules are assembled from dimers of α- and β-tubulin. These subunits are slightly acidic with an isoelectric point between 5.2 and 5.8.

Tubulin was long thought to be specific to eukaryotes. Recently, however, the prokaryotic cell division protein FtsZ was shown to be evolutionarily related to tubulin.

Contents 1 α-tubulin and β-tubulin 2 γ-tubulin 3 δ and ε tubulin 4 Pharmacology 5 See also 6 External links

To form microtubules, the dimers of α- and β-tubulin bind to GTP and assemble onto the (+) ends of microtubules while in the GTP-bound state. After being incorporated into the microtubule, the bound molecule of GTP will hydrolyse into GDP.

Although both subunits bind GTP, only the β-subunit has GTPase activity; that is, β-tubulin can hydrolyse GTP to GDP whereas α-tubulin cannot. Whether the β-tubulin member of the tubulin dimer is bound to GTP or GDP influences the stability of the dimer in the microtubule.

Dimers bound to GTP tend to assemble into microtubules, while dimers bound to GDP tend to fall apart; thus, this GTP cycle is essential for the dynamic instability of the microtubule.

Class III β-tubulin‎ is a microtubule element expressed exclusively in neurons, and is a popular identifier specific for neurons in nervous tissue.

Katanin is a protein complex that severs β-tubulin, and is necessary for rapid microtubule transport in neurons and in higher plants.

γ-tubulin, another member of the tubulin family, is important in the nucleation and polar orientation of microtubules. It is found primarily in centrosomes and spindle pole bodies, since these are the areas of most abundant microtubule nucleation. In these organelles, several γ-tubulin and other protein molecules are found in complexes known as γ-tubulin ring complexes (γ-TuRCs), which chemically mimic the (+) end of a microtubule and thus allow microtubules to bind. γ-tubulin also has been isolated as a dimer and as a part of a γ-tubulin small complex (γTuSC), intermediate in size between the dimer and the γTuRC. γ-tubulin is the best understood mechanism of microtubule nucleation, but certain studies have indicated that certain cells may be able to adapt to its absence, as indicated by mutation and RNAi studies that have inhibited its correct expression.

Delta (δ) and epsilon (ε) tubulin have been found to localize at centrioles and may play a role in forming the mitotic spindle during mitosis, though neither is as well-studied as the α- and β- forms.

Tubulins are targets for anticancer drugs like Taxol® and the "Vinca alkaloid" drugs such as vinblastine and vincristine. The anti-gout agent colchicine binds to tubulin and inhibits microtubule formation, arresting neutrophil motility and decreasing inflammation.

• Microtubule
• Cytoskeleton
• Motor protein
• Kinesin
• Dynein
• FtsZ
• Tubulin, beta 2A

• MeSH Tubulin
• EC 3.6.5.6

v • d • e Proteins of the cytoskeleton
Microfilaments	Actins - Actin-binding proteins - Actinin - Arp2/3 complex - Cofilin - Destrin - Gelsolin - Myosins - Profilin - Tropomodulin - Troponin (T, C, I) - Tropomyosin - Wiskott-Aldrich syndrome protein
Intermediate filaments	type 1 and 2 (Cytokeratin, type I, type II) - type 3 (Desmin, GFAP, Peripherin, Vimentin) - type 4 (Internexin, Nestin, Neurofilament, Synemin, Syncoilin) - type 5 (Lamin A, B)
Microtubules	Dyneins - Kinesins - MAPs (Tau protein, Dynamin) - Tubulins - Stathmin - Tektin
Catenins	Alpha catenin - Beta catenin - Plakoglobin (gamma catenin) - Delta catenin
Nonhuman	Major sperm proteins - Prokaryotic cytoskeleton (Crescentin, FtsZ, MreB)
Other	APC - Dystrophin (Dystroglycan) - plakin (Desmoplakin, Plectin) - Spectrin - Talin - Utrophin - Vinculin

v • d • e Acid anhydride hydrolases: GTPases/G proteins (EC 3.6.5)
3.6.5.1: Heterotrimeric G protein	Gαs - Gαi - Gαq/11 - Gα12/13 - Transducin
3.6.5.2: Small GTPase	Ras - Rab (Rab27) - Arf (Arf6) - Ran - Rheb - Rho (RhoA, RhoB, CDC42, Rac1) - Rap
3.6.5.3: Elongation factor	Prokaryotic - Eukaryotic
3.6.5.5-6: Other	Dynamin (is a GTPase, is not a G protein) - Tubulin