Insect toxins
Encyclopedia
Insect toxins are various protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

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

s produced by insect species.

Assassin bugs
Reduviidae
Reduviidae is a large, cosmopolitan family of predatory insects in the suborder Heteroptera...

, sometimes known as kissing bugs, are one of the largest and morphologically diverse families of true bugs feeding on cricket
Cricket
Cricket is a bat-and-ball game played between two teams of 11 players on an oval-shaped field, at the centre of which is a rectangular 22-yard long pitch. One team bats, trying to score as many runs as possible while the other team bowls and fields, trying to dismiss the batsmen and thus limit the...

s, caterpillar
Caterpillar
Caterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...

s and other insects. Some assassin bug species are bloodsucking parasites of mammals, even feed on humans. They can be commonly found throughout most of the world and their size varies from a few millimeters to as much as 3 or 4 centimeters. The toxic saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...

 of the predatory assassin bugs contains a complex mixture of small and large peptides for diverse uses such as immobilizing and pre-digesting their prey, as well as defense against competitors and predators. Assassin bug toxins are small peptides with disulfide connectivity that target 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...

s. They are relatively homologous to the calcium channel blockers omega-conotoxin
Conotoxin
A conotoxin is one of a group of neurotoxic peptides isolated from the venom of the marine cone snail, genus Conus.Conotoxins, which are peptides consisting of 10 to 30 amino acid residues, typically have one or more disulfide bonds. Conotoxins have a variety of mechanisms of actions, most of...

s from marine cone snails and belong to the four-loop cysteine scaffold structural class.

One of these small proteins, Ptu1, blocks reversibly the N-type calcium channels, but at the same time is less specific for the L- or P/Q-type calcium channels. Ptu1 is 34 amino acid residues long and is cross-linked by 3 disulfide bridges. Ptu1 contains a beta-sheet region made of 2 antiparallel beta-strands and consists of a compact disulfide-bonded core from which four loops emerge as well as N- and C-termini. Some assassin bug toxins are listed below:
  • Agriosphodrus dohrni toxin Ado1.
  • Isyndus obscurus toxin Iob1.
  • Peirates turpis toxin Ptu1.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK