One scorpion, two venoms: Prevenom of Parabuthus
transvaalicus acts as an alternative type of venom
with distinct mechanism of action
Scorpion venom is a complex mixture of salts, small molecules,
peptides, and proteins. Scorpions employ this valuable tool in
several sophisticated ways for subduing prey, deterring predators,
and possibly during mating. Here, a subtle but clever strategy of
venom utilization by scorpions is reported. Scorpions secrete a
small quantity of transparent venom when initially stimulated that
we propose to name prevenom. If secretion continues, a cloudy
and dense venom that is white in color is subsequently released.
The prevenom contains a combination of high K salt and several
peptides including some that block rectifying K channels and elicit
significant pain and toxicity because of a massive local depolarization.
The presence of high extracellular K in the prevenom can
depolarize cells and also decrease the local electrochemical gradient
making it more difficult to reestablish the resting potential.
When this positive change to the K equilibrium potential is
combined with the blockage of rectifying K channels, this further
delays the recovery of the resting potential, causing a prolonged
effect. We propose that the prevenom of scorpions is used as a
highly efficacious predator deterrent and for immobilizing small
prey while conserving metabolically expensive venom until a
certain level of stimuli is reached, after which the venom is
secreted.
Like the snails of the genus Conus , scorpions have
developed efficient venoms. They occupy temperate and
tropical habitats of the world. They are especially well adapted
to survive in extreme thermal environments, sometimes constituting
a major portion of the total animal biomass in these
environments . Scorpions are considered among the successful
inhabitants of earth . Although numerous factors contribute
to the success of scorpions, perhaps the ability to produce
and deliver a highly toxic secretion, the venom, is an important
determinant in this success. Venom is used by scorpions to
subdue prey and also as a defense against predators. Although
all scorpion species are known to possess venom, only about
25–50 of 1,250 known species are considered medically important
The scorpion venom, a unique weapon, is a secretion composed
of water, salts, small molecules, peptides, and proteins .
The venoms of several scorpion species have been well characterized,
and peptides possess the majority of the biological
activity . In the venom mixture, there are peptides that are
specialized against vertebrates, invertebrates, or active against
both. Members of all three groups are well characterized and
include peptides that target all of the major ion channel types
such as Na , K , Cl , Ca2 , and ryanodine-sensitive Ca2
channels . The devastating potency of the venom is caused
by its ability to target multiple types of ion channels simultaneously,
resulting in a massive and recurring depolarization that
disables or kills the prey or predator.
Production and storage of protein-rich venom is undoubtedly
an expensive metabolic investment, especially for species
adapted to survive in extreme ecosystems on scarce resources.
Other than the antimicrobial peptides, almost all neurotoxins in
the venom are reported to be highly folded, disulfide-bridged
molecules . Low yields of expression of these peptides in
recombinant systems also hint at the unique and difficult folding
and storage requirements . However, used sparingly, venom
is an excellent tool for both offense and defense. A study on
the sting use of Parabuthus species is a good example of the
regulation of sting use according to prey size, demonstrating the
conservative use of venom . The conservative use of venom
by many species of scorpions suggests that venom secretion is
also regulated.
BIOCHEMISTRY
secrete an ‘‘opaque’’ venom, which is white in color and loaded
with toxins at 53–85 mg ml protein concentration (Fig. 1B).
Prevenom constitutes 5% of the secreted venom in volume
(Table 1). In some cases where the individual scorpion is
aggressive, it is difficult to obtain prevenom separately from
venom. By the time these scorpions are restrained, they start
secreting the venom. However, even in these cases, it is possible
to observe prevenom venom mixture during the milking process,
during which the clear and cloudy portions mix slowly on the side
of the microfuge tube.Prevenom Is Active Against both Insects and Mammals.
transvaalicus acts as an alternative type of venom
with distinct mechanism of action
Scorpion venom is a complex mixture of salts, small molecules,
peptides, and proteins. Scorpions employ this valuable tool in
several sophisticated ways for subduing prey, deterring predators,
and possibly during mating. Here, a subtle but clever strategy of
venom utilization by scorpions is reported. Scorpions secrete a
small quantity of transparent venom when initially stimulated that
we propose to name prevenom. If secretion continues, a cloudy
and dense venom that is white in color is subsequently released.
The prevenom contains a combination of high K salt and several
peptides including some that block rectifying K channels and elicit
significant pain and toxicity because of a massive local depolarization.
The presence of high extracellular K in the prevenom can
depolarize cells and also decrease the local electrochemical gradient
making it more difficult to reestablish the resting potential.
When this positive change to the K equilibrium potential is
combined with the blockage of rectifying K channels, this further
delays the recovery of the resting potential, causing a prolonged
effect. We propose that the prevenom of scorpions is used as a
highly efficacious predator deterrent and for immobilizing small
prey while conserving metabolically expensive venom until a
certain level of stimuli is reached, after which the venom is
secreted.
Like the snails of the genus Conus , scorpions have
developed efficient venoms. They occupy temperate and
tropical habitats of the world. They are especially well adapted
to survive in extreme thermal environments, sometimes constituting
a major portion of the total animal biomass in these
environments . Scorpions are considered among the successful
inhabitants of earth . Although numerous factors contribute
to the success of scorpions, perhaps the ability to produce
and deliver a highly toxic secretion, the venom, is an important
determinant in this success. Venom is used by scorpions to
subdue prey and also as a defense against predators. Although
all scorpion species are known to possess venom, only about
25–50 of 1,250 known species are considered medically important
The scorpion venom, a unique weapon, is a secretion composed
of water, salts, small molecules, peptides, and proteins .
The venoms of several scorpion species have been well characterized,
and peptides possess the majority of the biological
activity . In the venom mixture, there are peptides that are
specialized against vertebrates, invertebrates, or active against
both. Members of all three groups are well characterized and
include peptides that target all of the major ion channel types
such as Na , K , Cl , Ca2 , and ryanodine-sensitive Ca2
channels . The devastating potency of the venom is caused
by its ability to target multiple types of ion channels simultaneously,
resulting in a massive and recurring depolarization that
disables or kills the prey or predator.
Production and storage of protein-rich venom is undoubtedly
an expensive metabolic investment, especially for species
adapted to survive in extreme ecosystems on scarce resources.
Other than the antimicrobial peptides, almost all neurotoxins in
the venom are reported to be highly folded, disulfide-bridged
molecules . Low yields of expression of these peptides in
recombinant systems also hint at the unique and difficult folding
and storage requirements . However, used sparingly, venom
is an excellent tool for both offense and defense. A study on
the sting use of Parabuthus species is a good example of the
regulation of sting use according to prey size, demonstrating the
conservative use of venom . The conservative use of venom
by many species of scorpions suggests that venom secretion is
also regulated.
BIOCHEMISTRY
secrete an ‘‘opaque’’ venom, which is white in color and loaded
with toxins at 53–85 mg ml protein concentration (Fig. 1B).
Prevenom constitutes 5% of the secreted venom in volume
(Table 1). In some cases where the individual scorpion is
aggressive, it is difficult to obtain prevenom separately from
venom. By the time these scorpions are restrained, they start
secreting the venom. However, even in these cases, it is possible
to observe prevenom venom mixture during the milking process,
during which the clear and cloudy portions mix slowly on the side
of the microfuge tube.Prevenom Is Active Against both Insects and Mammals.
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