The amino acid sequence of Iberiotoxin
Pyr - Phe - Thr - Asp - Val - Asp - Cys - Ser - Val - Ser - Lys - Glu - Cys - Trp - Ser - Val - Cys - Lys - Asp - Leu - Phe - Gly - Val - Asp - Arg - Gly - Lys - Cys - Met - Gly - Lys - Lys - Cys - Arg - Cys - Tyr - Gln - OH
Disulfide bridges: Cys7 - Cys28, Cys13 - Cys33, Cys17 - Cys35

Iberiotoxin is an ion channel

Ion channel

Ion channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells...

 toxin

Toxin

A toxin is a poisonous substance produced within living cells or organisms; man-made substances created by artificial processes are thus excluded...

 purified from the Eastern Indian red scorpion

Scorpion

Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...

 Buthus tamulus.
Iberiotoxin selectively inhibits the current

Electric current

Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...

 through large-conductance calcium-activated potassium channel

Calcium-activated potassium channel

Calcium-activated potassium channels are divided into BK channels, IK channels, and SK channels based on their conductance ....

s.

Chemistry

Iberiotoxin is a 37-amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

 peptide

Peptide

Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...

. It is also known as "Potassium channel toxin alpha-KTx 1.3" or IbTx. The complete amino acid

Amino acid

Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...

 sequence has been defined and it displays 68% sequence homology with charybdotoxin

Charybdotoxin

Charybdotoxin is a 37 amino acid neurotoxin from the venom of the scorpion Leiurus quinquestriatus hebraeus that blocks calcium-activated potassium channels. This blockade causes hyperexcitability of the nervous system.-Chemical properties:...

.

Target and mode of action

Iberiotoxin binds to the outer face of the large-conductance calcium-activated potassium channels (maxiK or BK channel

BK channel

BK channels , also called Maxi-K or slo1, are ion channels characterized by their large conductance of potassium ions through cell membranes. These channels are activated by changes in membrane electrical potential and/or by increases in concentration of intracellular calcium ion...

s) with high affinity (Kd ~1 nM). It selectively inhibits the current by decreasing both the probability of opening and the open time of the channel.

Toxicity

The venom produces mainly cardiopulmonary abnormalities like circulatory derangements, myocarditis

Myocarditis

Myocarditis is inflammation of heart muscle . It resembles a heart attack but coronary arteries are not blocked.Myocarditis is most often due to infection by common viruses, such as parvovirus B19, less commonly non-viral pathogens such as Borrelia burgdorferi or Trypanosoma cruzi, or as a...

 and changes in cardiac sarcolemma

Sarcolemma

The sarcolemma is the cell membrane of a muscle cell . It consists of a true cell membrane, called the plasma membrane, and an outer coat made up of a thin layer of polysaccharide material that contains numerous thin collagen fibrils...

l ATPase

ATPase

ATPases are a class of enzymes that catalyze the decomposition of adenosine triphosphate into adenosine diphosphate and a free phosphate ion. This dephosphorylation reaction releases energy, which the enzyme harnesses to drive other chemical reactions that would not otherwise occur...

 and by these abnormalities it can finally cause death. In rural India

India

India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...

 the scorpion and its venom is a commonly known factor of children's death. The venom initially causes transient cholinergic

Cholinergic

The word choline generally refers to the various quaternary ammonium salts containing the N,N,N-trimethylethanolammonium cation. Found in most animal tissues, choline is a primary component of the neurotransmitter acetylcholine and functions with inositol as a basic constituent of lecithin...

 stimulation (vomiting, profuse sweating

Sweating

Perspiration is the production of a fluid consisting primarily of water as well as various dissolved solids , that is excreted by the sweat glands in the skin of mammals...

, bradycardia

Bradycardia

Bradycardia , in the context of adult medicine, is the resting heart rate of under 60 beats per minute, though it is seldom symptomatic until the rate drops below 50 beat/min. It may cause cardiac arrest in some patients, because those with bradycardia may not be pumping enough oxygen to their heart...

, priapism

Priapism

Priapism is a potentially harmful and painful medical condition in which the erect penis or clitoris does not return to its flaccid state, despite the absence of both physical and psychological stimulation, within four hours. There are two types of priapism: low-flow and high-flow. Low-flow...

, hypersalivation

Hypersalivation

Hypersalivation is excessive production of saliva. It has also been defined as increased amount of saliva in the mouth, which may also be caused by decreased clearance of saliva....

, and hypotension

Hypotension

In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...

) which is followed by sustained adrenergic

Adrenergic

An adrenergic agent is a drug, or other substance, which has effects similar to, or the same as, epinephrine . Thus, it is a kind of sympathomimetic agent...

 hyperactivity (hypertension

Hypertension

Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

, tachycardia

Tachycardia

Tachycardia comes from the Greek words tachys and kardia . Tachycardia typically refers to a heart rate that exceeds the normal range for a resting heart rate...

, and myocardial failure). The adrenergic phase but not the cholinergic phase is a dose-dependent phenomenon.

Treatment

Treatment is mainly symptomatic. Local pain

Pain

Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...

 is treated by injecting dehydroemetine

Dehydroemetine

Dehydroemetine is a synthetically produced antiprotozoal agent similar to emetine in its anti-amoebic properties and structure , but it produces fewer side effects...

 at the site of the sting. Hypovolaemia is corrected by oral rehydration solution. Agitated, confused and non-cooperative patients are given a 5% dextrose saline

Saline (medicine)

In medicine, saline is a general term referring to a sterile solution of sodium chloride in water but is only sterile when it is to be placed intravenously, otherwise, a saline solution is a salt water solution...

 drip. Patients with hypertension

Hypertension

Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

 on admission are given a single dose of 5 mg sublingual

Sublingual

Sublingual, literally 'under the tongue', from Latin, refers to the pharmacological route of administration by which drugs diffuse into the blood through tissues under the tongue...

 nifedipine

Nifedipine

Nifedipine is a dihydropyridine calcium channel blocker...

 and oral prazosin

Prazosin

Prazosin, trade names Minipress, Vasoflex, Pressin and Hypovase, is a sympatholytic drug used to treat high blood pressure and Anxiety, PTSD and Panic Disorder. It belongs to the class of alpha-adrenergic blockers. Specifically, prazosin is selective for the alpha-1 receptors on vascular smooth...

. The blood pressure in patients with hypertension is controlled with sublingual nifedipine alone. Patients with pulmonary oedema are propped up and given intravenous aminophylline

Aminophylline

Aminophylline is a bronchodilator. It is a compound of the bronchodilator theophylline with ethylenediamine in 2:1 ratio. The ethylenediamine improves solubility, and the aminophylline is usually found as a dihydrate-Properties:...

, intravenous sodium bicarbonate

Intravenous sodium bicarbonate

Intravenous sodium bicarbonate is a solution for intravenous administration that increases plasma bicarbonate, buffers excess hydrogen ion concentration, raises blood pH and reverses the clinical manifestations of acidosis....

, oral prazosin

Prazosin

Prazosin, trade names Minipress, Vasoflex, Pressin and Hypovase, is a sympatholytic drug used to treat high blood pressure and Anxiety, PTSD and Panic Disorder. It belongs to the class of alpha-adrenergic blockers. Specifically, prazosin is selective for the alpha-1 receptors on vascular smooth...

, and oxygen

Oxygen

Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

by mask.