biology

LuxR-type DNA-binding HTH domain

LuxR-type DNA-binding HTH 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 LuxR-type DNA-binding HTH domain rather than just read about it. In short: In molecular biology, the LuxR-type DNA-binding HTH domain is a DNA-binding, helix-turn-helix (HTH) domain of about 65 amino acids. It is present in transcription regulators of the LuxR/FixJ family of response regulators.

Key takeaways

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Reference excerpt

In molecular biology, the LuxR-type DNA-binding HTH domain is a DNA-binding, helix-turn-helix (HTH) domain of about 65 amino acids. It is present in transcription regulators of the LuxR/FixJ family of response regulators. The domain is named after Vibrio fischeri luxR, a transcriptional activator for quorum-sensing control of luminescence. LuxR-type HTH domain proteins occur in a variety of organisms. The DNA-binding HTH domain is usually located in the C-terminal region of the protein; the N-terminal region often containing an autoinducer-binding domain or a response regulatory domain. Most luxR-type regulators act as transcription activators, but some can be repressors or have a dual role for different sites. LuxR-type HTH regulators control a wide variety of activities in various biological processes. The luxR-type, DNA-binding HTH domain forms a four-helical bundle structure. The HTH motif comprises the second and third helices, known as the scaffold and recognition helix, respectively. The HTH binds DNA in the major groove, where the N-terminal part of the recognition helix makes most of the DNA contacts. The fourth helix is involved in dimerisation of gerE and traR. Signalling events by one of the four activation mechanisms described below lead to multimerisation of the regulator. The regulators bind DNA as multimers. LuxR-type HTH proteins can be activated by one of four different mechanisms: 1. Regulators which belong to a two-component sensory transduction system where the protein is activated by its phosphorylation, generally on an aspartate residue, by a transmembrane kinase. Some proteins that belong to this category are:

Rhizobiaceae fixJ (global regulator inducing expression of nitrogen-fixation genes in microaerobiosis) Escherichia coli and Salmonella typhimurium uhpA (activates hexose phosphate transport gene uhpT) E. coli narL and narP (activate nitrate reductase operon) Enterobacteria rcsB (regulation of exopolysaccharide biosynthesis in enteric and plant pathogenesis) Bordetella pertussis bvgA (virulence factor) Bacillus subtilis comA (involved in expression of late-expressing competence genes) 2. Regulators which are activated, or in very rare cases repressed, when bound to N-acyl homoserine lactones, which are used as quorum sensing molecules in a variety of Gram-negative bacteria:

Vibrio fischeri luxR (activates bioluminescence operon) Agrobacterium tumefaciens traR (regulation of Ti plasmid transfer) Erwinia carotovora carR (control of carbapenem antibiotics biosynthesis) E. carotovora expR (virulence factor for soft rot disease; activates plant tissue macerating enzyme genes) Pseudomonas aeruginosa lasR (activates elastase gene lasB) Erwinia chrysanthemi echR and Erwinia stewartii esaR Pseudomonas chlororaphis phzR (positive regulator of phenazine antibiotic production) Pseudomonas aeruginosa rhlR (activates rhlAB operon and lasB gene) Acinetobacter baumannii abaR (activates operon for production of surfactant-like lipopeptide acinetin-505) 3. Autonomous effector domain regulators, without a regulatory domain, represented by gerE.

B. subtilis gerE (transcription activator and repressor for the regulation of spore formation) 4. Multiple ligand-binding regulators, exemplified by malT.

E. coli malT (activates maltose operon; MalT binds ATP and maltotriose)

References

Illustrations

Worked examples

Example 1 — a first encounter with LuxR-type DNA-binding HTH domain

Start with the simplest possible case. Write down what LuxR-type DNA-binding HTH 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 LuxR-type DNA-binding HTH 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 LuxR-type DNA-binding HTH 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 LuxR-type DNA-binding HTH domain

In research: LuxR-type DNA-binding HTH 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 LuxR-type DNA-binding HTH 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: LuxR-type DNA-binding HTH 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 LuxR-type DNA-binding HTH 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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Frequently asked questions

What is LuxR-type DNA-binding HTH domain in simple terms?

Why does LuxR-type DNA-binding HTH 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 LuxR-type DNA-binding HTH 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 LuxR-type DNA-binding HTH domain.