Some tarantula toxins interfere with channel proteins in cell membranes — and are therefore useful tools to study how these proteins work.
Venomous animals like tarantulas or scorpions inject their prey with toxins to disable them. Some of these toxins work by altering the activity of proteins called ion channels, which are found within membranes in cells. These channels can allow potassium ions and/or other ions to pass through the membrane and have many important roles. For example, ion channels are involved in heart muscle contraction and allow information to travel between brain cells.
Researchers have used some of the toxins as tools to study how ion channel proteins operate. For example, a toxin produced by tarantulas called psalmotoxin binds to a type of ion channel called the acid-sensing ion channels (ASIC). Researchers have previously been able to visualize the three-dimensional structure of psalmotoxin attached to ASIC, which revealed how the toxin binds to and alters the activity of the ion channel.
Another tarantula toxin called guangxitoxin is very similar to psalmotoxin, but it binds to a different type of potassium ion channel. It is thought that guangxitoxin binds to a site on these ion channels that is deep within the membrane, but it is not clear how this works. Now, Kanchan Gupta, Maryam Zamanian, Chanhyung Bae and co-workers have compared some of the structural and chemical properties of the two toxins.
The experiments show that both toxins interact with the membrane to enable them to bind with their target ion channels. However, guangxitoxin moves deeper into the interior of the membrane. Also, Gupta, Zamanian, Bae and co-workers’ findings suggest that both toxins use a similar surface that curves inwards to clamp onto their target ion channels. This common structural feature will be useful for designing experiments to visualize the three-dimensional structure of guangxitoxin bound to a potassium ion channel.
To find out more
Read the eLife research paper on which this eLife Digest is based: “Tarantula toxins use common surfaces for interacting with Kv and ASIC ion channels ” (May 7, 2015).
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