# Does tetrodotoxin look like something in the body?

1. ### jackmell

Blue-ring octopus' have this. It binds to Na channels in nerve cells.

I don't know if you guys know this in here about biochemistry, but it includes a marvelous story of mimicry.

Anyways, I was just wondering if tetrodotoxin looks like something, in the same way that LSD looks like dopamine. Didn't say anything about mimicry in Wikipedia but they just might not know.

2. ### SW VandeCarr

What you are asking, I think, is does the body provide a natural compound that could competitively block TTX at the neurotoxic receptor site 1 (NXR1)? I doubt it, at least not in sufficient quantities that would be effective. Otherwise TTX wouldn't be so toxic. However there is a class of peptides which does bind to NXR1 and could possibly block TTX. They're are called $\mu$-conopeptides and their interaction with NXR1 neurotoxins is complex, so I would stay away from the Blue Ring Octopus and other TTX making creatures for the time being. The issue isn't so much how the whole molecule looks, but how that portion of the molecule presented to the receptor site looks.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2920548/

Last edited: Jul 1, 2013
1 person likes this.
3. ### jackmell

Hi. Thanks for that. Fascinating subject. Here's a quote:

"TTX is thought to occupy a site within the vestibule of the ion channel near the extracellular end of the channel pore, and, by binding to this site, to occlude the permeation pathway of sodium ions through the pore."

I suppose perhaps I don't understand the physiology well enough. I thought the gate was normally controlled by various molecules which open and close it and that maybe TTX, or a particular part of TTX resembled the active end of the normal molecule which closed it and had a greater affinity to the active site so thus blocked the normal agent from controlling the gate.

4. ### SW VandeCarr

The sodium channel has both a pore and a gate, although they work closely together. TTX apparently physically blocks the pore superseding the gating function. Voltage gated channels typically are selective for sodium, potassium or calcium. Ion filtering is a function of the pore. The gate closes to ion flux with inactivation of the channel as during the refractory period following an action potential.

http://jp.physoc.org/content/590/11/2577.full.pdf+html

Last edited: Jul 2, 2013
Know someone interested in this topic? Share a link to this question via email, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted