biology

KIX domain

KIX 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 KIX domain rather than just read about it. In short: In biochemistry, the KIX domain (kinase-inducible domain (KID) interacting domain) or CREB binding domain is a protein domain of the eukaryotic transcriptional coactivators CBP and P300. It serves as a docking site for the formation of heterodimers between the coactivator and specific transcription factors.

Key takeaways

KIX 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 KIX domain to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of KIX domain from memory before moving on to harder problems.

Reference excerpt

In biochemistry, the KIX domain (kinase-inducible domain (KID) interacting domain) or CREB binding domain is a protein domain of the eukaryotic transcriptional coactivators CBP and P300. It serves as a docking site for the formation of heterodimers between the coactivator and specific transcription factors. Structurally, the KIX domain is a globular domain consisting of three α-helices and two short 310-helices. The KIX domain was originally discovered in 1996 as the specific and minimal region in CBP that binds and interacts with phosphorylated CREB to activate transcription. It was thus first termed CREB-binding domain. However, when it was later discovered that it also binds many other proteins, the more general name KIX domain became favoured. The KIX domain contains two separate binding sites: the "c-Myb site", named after the oncoprotein c-Myb, and the "MLL site", named after the proto-oncogene MLL (Mixed Lineage Leukemia, KMT2A). The paralogous coactivators CBP (CREBBP) and P300 (EP300) are recruited to DNA-bound transcription factors to activate transcription. Coactivators can associate with promoters and enhancers in the DNA only indirectly through protein-protein contacts with transcription factors. CBP and P300 activate transcription synergistically in two ways: first, by remodelling and relaxing chromatin through their intrinsic histone acetyltransferase activity, and second, by recruiting the basal transcription machinery, such as RNA polymerase II. The KIX domain belongs to the proposed GACKIX domain superfamily. GACKIX comprises structurally and functionally highly homologous domains in related proteins. It is named after the protein GAL11 / ARC105 (MED15), the plant protein CBP-like, and the KIX domain from CBP and P300. Additional instances include RECQL5 and related plant proteins. All of these contain a KIX domain or KIX-related domain that interacts with the transactivation domain of many different transcription factors. The distinction between a KIX domain, a KIX-related domain and a GACKIX domain is subject to an ongoing debate and not clearly defined.

The full CBP/P300 protein

Aside from the KIX domain, CBP and P300 contain many other protein binding domains that should not be confused (numbers are aa numberings):

CH1/TAZ1 domain, CBP[347–433], P300[323-423] KIX domain, CBP[587–666], P300[566–645] Bromodomain, CBP[1103–1175], P300[1067–1139] CH2 domain (IPR010303), CBP[1191–1317], P300[1155-1280]. HAT domain, CBP[1323–1700], P300[1287–1663] CH3/ZZ domain, CBP[1701-1744], P300[1664-1707] CH3/TAZ2 domain, CBP[1765–1846], P300[1728-1809] IRF-3 binding (i-BiD), nuclear receptor coactivator binding (NCBD), or SRC1 interaction domain (SID; IPR014744), CBP[2020-2113], P300[1992-2098]. All three CH (cysteine/histidine-rich) domains are zinc fingers.

Interactions

Human and animal proteins:

Yeast proteins:

Viral proteins:

References

External links KIXBASE, a database of KIX-superfamily domains and PDB structures (HMM training dataset)

Illustrations

Worked examples

Example 1 — a first encounter with KIX domain

Start with the simplest possible case. Write down what KIX 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 KIX 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 KIX 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 KIX domain

In research: KIX 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 KIX 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: KIX domain is common in secondary-school and first-year university syllabi. It links to neighbouring topics Gene expression, Protein domains, so understanding it makes those chapters shorter.
In everyday life: Look for KIX 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study KIX domain in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what KIX 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 KIX domain out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is KIX domain in simple terms?

Why does KIX 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 KIX 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 KIX domain.