paralysis and the resulting suffocation. Whales and other marine
animals have been known to die from PSP after consuming sufficient
quantities either of dinoflagellates or of other animals that have
themselves consumed STX-containing dinoflagellates. PSP is probably
a bigger problem for whales and other marine animals than it is for
people.
Like TTX, STX is a hydrophilic molecule and does not cross the
blood-brain barrier. And as for TTX, the treatment for STX poisoning
is artificial respiration until the effects of the poison dissipate as the
STX is gradually eliminated from the body.
As with TTX resistance, there are also cases where variation in the
structure of the voltage-gated sodium channel will dramatically de-
crease sensitivity to STX. One compelling example has been studied in
a variety of clam living in regions where there are frequent dinoflag-
ellate blooms. The clam has a sodium channel variant that is much
less sensitive to the blocking effects of STX. Moreover, it is impressive
that this reduced sensitivity results from a single amino acid change
in a particular position in the structure of the protein. The amino acid
change is from glutamic acid to aspartic acid, two very closely related
molecules.
O oO Oo
AWK HO OH wy^0 OHNH2 OH NH2
Glutamic acid Aspartic acidThis highlights the dramatic sensitivity of protein function to very
tiny structural changes, if the changes occur in just the right way.
Another example of a poison that works by messing with voltage-