53 research outputs found
New Gastropod Vectors and Tetrodotoxin Potential Expansion in Temperate Waters of the Atlantic Ocean
Tetrodotoxin is a potent low weight marine toxin found in warm waters, especially of the Indian and Pacific Oceans. Intoxications are usually linked to the consumption of the puffer fish, although TTX was already detected in several different edible taxa. Benthic organisms such as mollusks and echinoderms, with different feeding habits, were collected monthly along the Portuguese coast from the summer of 2009 until the end of 2010. The extraction and analysis techniques were optimized and TTX and some analogues were detected for the first time in two intertidal gastropod species—Gibbula umbilicalis and Monodonta lineata by LC-MS/MS and UPLC-MS/MS. Although the levels are low, these findings suggest that monitoring of TTX and analogues in North Atlantic species should be implemented so as to detect potentially new toxin vectors and seasonal and/or geographical patterns
The Tetrodotoxin Binding Site Is within the Outer Vestibule of the Sodium Channel
Tetrodotoxin and saxitoxin are small, compact asymmetrical marine toxins that block voltage-gated Na channels with high affinity and specificity. They enter the channel pore’s outer vestibule and bind to multiple residues that control permeation. Radiolabeled toxins were key contributors to channel protein purification and subsequent cloning. They also helped identify critical structural elements called P loops. Spacial organization of their mutation-identified interaction sites in molecular models has generated a molecular image of the TTX binding site in the outer vestibule and the critical permeation and selectivity features of this region. One site in the channel’s domain I P loop determines affinity differences in mammalian isoforms
Neurotoxic Alkaloids: Saxitoxin and Its Analogs
Saxitoxin (STX) and its 57 analogs are a broad group of natural neurotoxic alkaloids, commonly known as the paralytic shellfish toxins (PSTs). PSTs are the causative agents of paralytic shellfish poisoning (PSP) and are mostly associated with marine dinoflagellates (eukaryotes) and freshwater cyanobacteria (prokaryotes), which form extensive blooms around the world. PST producing dinoflagellates belong to the genera Alexandrium, Gymnodinium and Pyrodinium whilst production has been identified in several cyanobacterial genera including Anabaena, Cylindrospermopsis, Aphanizomenon Planktothrix and Lyngbya. STX and its analogs can be structurally classified into several classes such as non-sulfated, mono-sulfated, di-sulfated, decarbamoylated and the recently discovered hydrophobic analogs—each with varying levels of toxicity. Biotransformation of the PSTs into other PST analogs has been identified within marine invertebrates, humans and bacteria. An improved understanding of PST transformation into less toxic analogs and degradation, both chemically or enzymatically, will be important for the development of methods for the detoxification of contaminated water supplies and of shellfish destined for consumption. Some PSTs also have demonstrated pharmaceutical potential as a long-term anesthetic in the treatment of anal fissures and for chronic tension-type headache. The recent elucidation of the saxitoxin biosynthetic gene cluster in cyanobacteria and the identification of new PST analogs will present opportunities to further explore the pharmaceutical potential of these intriguing alkaloids
Isolation of Polycavernoside D from a Marine Cyanobacterium
The polycavernosides make up a unique
class of marine-derived macrolides
that were implicated in the poisoning of 49 people in the South Western
Pacific resulting in 11 deaths. The original source ascribed to these
environmental toxins was from the edible red alga <i>Polycavernosa
tsudai</i> (also known as <i>Gracilaria edulis</i>);
however, the inability to reisolate these metabolites from the alga,
along with structural resemblance to several marine cyanobacterial
natural products, suggested that these compounds derive from these
latter photosynthetic prokaryotes. In this study, we identified a
new analogue “polycavernoside D” from an environmental
sample of the marine cyanobacterium <i>Okeania</i> sp.,
thus providing the first experimental evidence that these lethal toxins
are in fact cyanobacterial secondary metabolites. Moreover, the new
metabolite was obtained from a Caribbean cyanobacterial collection,
thus suggesting this toxin family to be of broader environmental occurrence
than previously realized, and raising concerns about unrecognized
human exposure in diverse tropical marine environments
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