science

Noxiustoxin

Noxiustoxin is a science 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 Noxiustoxin rather than just read about it. In short: Noxiustoxin (NTX) is a toxin from the venom of the Mexican scorpion Centruroides noxius Hoffmann which block voltage-dependent potassium channels and calcium-activated potassium channels. Sources NTX was first purified from homogenized crude venom extract of the Mexican scorpion Centruroides noxius Hoffmann, found in the Mexican state of Nayarit.

Key takeaways

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

Reference excerpt

Noxiustoxin (NTX) is a toxin from the venom of the Mexican scorpion Centruroides noxius Hoffmann which block voltage-dependent potassium channels and calcium-activated potassium channels.

Sources NTX was first purified from homogenized crude venom extract of the Mexican scorpion Centruroides noxius Hoffmann, found in the Mexican state of Nayarit. NTX accounts for only about 1% of the scorpion venom. NTX is one of the best-studied toxic peptides from scorpion venoms. It was the second purified toxin obtained from the genus Centruroides after neurotoxin II and the first short peptide from scorpion venom to be reported in the literature. The name for noxiustoxin was first proposed in 1982, before which it was known as toxin II-11

Chemistry NTX is a peptide consisting of 39 amino acid residues. It has a molar mass of 4195.06 and the following primary amino acid sequence: TIINVKCTSPKQCSKPCKELYGSSAGAKCMNGKCKCYNN-NH2. The sequence of NTX contains no histidine, arginine, tryptophan, or phenylalanine. NTX has three disulfide bridges (Cys7-Cys29, Cys13-Cys34, Cys17-Cys36) and contains an amidated C-terminus. NTX is similar in sequence to the margatoxin (79% identity), the kaliotoxin (51% identity), the charybdotoxin (49% identity), and the iberiotoxin (38% identity). The three-dimensional solution structure of NTX has been solved by nuclear magnetic resonance (NMR).

Target NTX blocks the pore of several types of voltage-gated K+ channels by reversibly binding to the channel receptor site. Furthermore, it affects calcium-activated potassium channels of skeletal muscles. In the squid axon, NTX was found to have relatively low binding affinity with their target site on the channel protein (KD = 300nM).

Mode of action NTX associates reversibly with K+ channels and thus decreases K+ permeability in brain synaptosomes. The location of the active site of NTX is not completely known yet. However, it is believed to be located close to the N-Terminal portion of the toxin as administration of synthetic-nonapeptide NTX1-9, which corresponds to the N-Terminal sequences of NTX, leads to symptoms of intoxication that are very similar to native NTX, while a second synthetic active fragment, corresponding to the C-Terminal of NTX, did not lead to symptoms of intoxication. Furthermore, the mode of action of NTX is thought to be concentration dependent. K+ currents are found to be blocked by NTX at concentrations lower than 1.5 μM in a voltage-independent manner and above 1.5 μM in a voltage-dependent manner. The blocking of K+ channels by NTX is never complete, which indicates that NTX is either not able to fully block a channel or that not all channels have a receptor site for NTX.

Toxicity LD50 of the venom is 0.26 μg/g in albino mice after intraperitoneal injection. Intoxication symptoms of mice include hyperexcitability, lacrimation, convulsions, salivation, dyspnea, and eventually death by respiratory paralysis.

Treatment Although the venom of Centruroides noxius Hoffmann is the most toxic of all the Mexican scorpions, it is less medically important, because Centruroides noxius does not cohabitate with humans

Medical significance It is suggested that due to structural similarity between toxins, a vaccine against Centruroides noxius could be efficient against other, more dangerous, Centruroides species that cause more public health problems.

References

External links https://www.ncbi.nlm.nih.gov/Structure/mmdb/mmdbsrv.cgi?Dopt=s&uid=74293 http://kaliumdb.org/toxins/86 https://www.ebi.ac.uk/pdbe/entry/pdb/1sxm

Illustrations

Worked examples

Example 1 — a first encounter with Noxiustoxin

Start with the simplest possible case. Write down what Noxiustoxin claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Noxiustoxin 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 Noxiustoxin 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 Noxiustoxin

In research: Noxiustoxin appears in science 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 Noxiustoxin 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: Noxiustoxin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ion channel toxins, Scorpion toxins, so understanding it makes those chapters shorter.
In everyday life: Look for Noxiustoxin 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 Noxiustoxin in 20 minutes

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

Frequently asked questions

What is Noxiustoxin in simple terms?

Noxiustoxin (NTX) is a toxin from the venom of the Mexican scorpion Centruroides noxius Hoffmann which block voltage-dependent potassium channels and calcium-activated potassium channels. Sources NTX was first purified from homogenized crude venom extract of the Mexican scorpion Centruroides noxius…

Why does Noxiustoxin matter?

Because it connects several science 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 Noxiustoxin?

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 Noxiustoxin.