biology

TBC domain

TBC domain is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand TBC domain rather than just read about it. In short: The TBC domain is an evolutionarily conserved protein domain found in all eukaryotes. It is approximately 180 to 200 amino acids long.

Key takeaways

TBC domain belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect TBC domain to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of TBC domain from memory before moving on to harder problems.

Reference excerpt

The TBC domain is an evolutionarily conserved protein domain found in all eukaryotes. It is approximately 180 to 200 amino acids long. The domain is named for its initial discovery in the proteins Tre-2, Bub2, and Cdc16. TBC family members act as GTPase-activating proteins (GAPs) for small GTPases in regulating the cell cycle. For example, Rab activity is modulated in part by GAPs, and many RabGAPs share a Tre2/Bub2/Cdc16(TBC)-domain architecture, suggesting that TBC domain-containing proteins may behave similarly.

Examples USP6 and CDC16 contain TBC domains. In addition, all proteins in the TBC family contain this domain:

Functions TBC mainly functions as a specific Rab GAP (GTPases activating proteins) by being used as tools to inactivate specific membrane trafficking events. GAPs serve to increase GTPase activity by contributing the residues to the active site and promoting conversion from GTP to GDP form. Such activity of TBC proteins does not always require a close physical interaction although few TBC proteins have shown clear GAP activity towards their binding Rabs. Rab families contribute to defining organelles and controlling specificity and rate of transport through individual pathways. Therefore, TBC Rab-GAPS are essential regulators of intracellular and membrane transports as well as central participants in signal transduction. Nevertheless, not all TBC may have a primary role as a Rab-GAP and conversely, not all Rab-GAP contain TBC. In addition, the fact that this family has been poorly studied makes it then further complicated.

Evolution and research Phylogenetic analysis has provided insight into the evolution of the TBC family. ScrollSaw was implemented as a recent strategy to overcome poor resolution between TBC genes found in standard phylogenetic strategies during initial reconstructions. Significantly, the TBC domain is nearly always smaller than the Rab cohort in any individual genome, suggesting Rab/TBC coevolution. Twenty-one putative TBC sub-classes were founded and identified as a seven robust and two moderately supported clades. Moreover, there has also been systematic analysis in order to identify the target Rabs of TBC proteins. It was, at first, based on the physical interaction between the TBC domain and its substrate Rab. For instance Barr and his coworkers found a specific interaction between RUTBC3/RabGAP-5 and Rab5A that activates the GTPase activity of Rab5 isoform. Similarly other research has shown that, among other important aspects, the TBC-Rab interaction alone is insufficient to determine the target of TBC proteins. However, there has been a second approach to identifying the target Rabs of TBC by investigating their in vitro GAP activity. Yet there has been similar discrepancies between this findings of different investigators which can be found in literature and may be attributable to differences between methods of in vitro. In addition, research has shown that TBC proteins are associated with some human diseases. For example, a dysfunction of TBC1D1 and TBC1D4 directly affects insulin actions and glucose uptake. Causing overweight or leanness due to the fact that this two family members of TBC regulate insulin-stimulated GLUT4 translocation to the plasma membrane in mammals. Furthermore, many of them have been shown to be associated with cancer, but the exact mechanism by which they are associated with this illness remains largely unknown. Therefore, there’s still much research needed to be done on this biological topic.

References

External links Fukuda M (2011). "TBC proteins: GAPs for mammalian small GTPase Rab?". Bioscience Reports. 31 (3): 159–68. doi:10.1042/BSR20100112. PMID 21250943. Gabernet-Castello C, O'Reilly AJ, Dacks JB, Field MC (2013). "Evolution of Tre-2/Bub2/Cdc16 (TBC) Rab GTPase-activating proteins". Molecular Biology of the Cell. 24 (10): 1574–83. doi:10.1091/mbc.E12-07-0557. PMC 3655817. PMID 23485563. Itoh T, Satoh M, Kanno E, Fukuda M (2006). "Screening for target Rabs of TBC (Tre-2/Bub2/Cdc16) domain-containing proteins based on their Rab-binding activity". Genes to Cells. 11 (9): 1023–37. doi:10.1111/j.1365-2443.2006.00997.x. PMID 16923123. Jackson TR, Brown FD, Nie Z, Miura K, Foroni L, Sun J, Hsu VW, Donaldson JG, Randazzo PA (2000). "ACAPs are arf6 GTPase-activating proteins that function in the cell periphery". The Journal of Cell Biology. 151 (3): 627–38. doi:10.1083/jcb.151.3.627. PMC 2185579. PMID 11062263. Pan X, Eathiraj S, Munson M, Lambright DG (2006). "TBC-domain GAPs for Rab GTPases accelerate GTP hydrolysis by a dual-finger mechanism". Nature. 442 (7100): 303–6. Bibcode:2006Natur.442..303P. doi:10.1038/nature04847. PMID 16855591. S2CID 4407126. Gabernet-Castello C, O'Reilly AJ, Dacks JB, Field MC (2013). "Evolution of Tre-2/Bub2/Cdc16 (TBC) Rab GTPase-activating proteins". Molecular Biology of the Cell. 24 (10): 1574–83. doi:10.1091/mbc.E12-07-0557. PMC 3655817. PMID 23485563. Albert S, Will E, Gallwitz D (1999). "Identification of the catalytic domains and their functionally critical arginine residues of two yeast GTPase-activating proteins specific for Ypt/Rab transport GTPases". The EMBO Journal. 18 (19): 5216–25. doi:10.1093/emboj/18.19.5216. PMC 1171592. PMID 10508155. Rueckert C, Haucke V (2012). "The oncogenic TBC domain protein USP6/TRE17 regulates cell migration and cytokinesis". Biology of the Cell. 104 (1): 22–33. doi:10.1111/boc.201100108. PMID 22188517. S2CID 5167674. Rowlands AG, Panniers R, Henshaw EC (1988). "The catalytic mechanism of guanine nucleotide exchange factor action and competitive inhibition by phosphorylated eukaryotic initiation factor 2". The Journal of Biological Chemistry. 263 (12): 5526–33. PMID 3356695. Rangaraju NS, Harris RB (1993). "GAP-releasing enzyme is a member of the pro-hormone convertase family of precursor protein processing enzymes". Life Sciences. 52 (2): 147–53. doi:10.1016/0024-3205(93)90134-o. PMID 8394962. Lamarche N, Hall A (1994). "GAPs for rho-related GTPases". Trends in Genetics. 10 (12): 436–40. doi:10.1016/0168-9525(94)90114-7. PMID 7871593.

Illustrations

TBC domain: The Rab cycle in membrane trafficking: The cycle between the GTP-bound inactive state and the GTP- bound active state is led by the Rab protein and regulated by an activating enzyme GEF[1] and an inactivating enzyme GAP which in this case could be the TBC protein. Hereafter, the activated form of Rab, GTP-bound, is incorporated to a specific organelle or vesicle and promotes its transport by interacting with a specific effector molecule. GTPase-activating proteins (GAPs) limit the duration of the active state and accelerate the slow intrinsic rate of GTP hydrolysis. — The Rab cycle in membrane trafficking: The cycle between the GTP-bound inactive state and the GTP- bound active state is led by the Rab protein and regulated by an activating enzyme GEF[1] and an inactivating enzyme GAP which in this case could be the TBC protein. Hereafter, the activated form of Rab, GTP-bound, is incorporated to a specific organelle or vesicle and promotes its transport by interacting with a specific effector molecule. GTPase-activating proteins (GAPs) limit the duration of the active state and accelerate the slow intrinsic rate of GTP hydrolysis.

Worked examples

Example 1 — a first encounter with TBC domain

Start with the simplest possible case. Write down what TBC domain claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to TBC domain before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about TBC domain ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of TBC domain

In research: TBC domain appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses TBC domain in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: TBC domain is common in secondary-school and first-year university syllabi. It links to neighbouring topics Protein domains, so understanding it makes those chapters shorter.
In everyday life: Look for TBC domain outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study TBC domain in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what TBC domain means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain TBC domain out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is TBC domain in simple terms?

The TBC domain is an evolutionarily conserved protein domain found in all eukaryotes. It is approximately 180 to 200 amino acids long.

Why does TBC domain matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study TBC domain?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on TBC domain.