Brevetoxin, the Dinoflagellate Neurotoxin, Localizes to Thylakoid Membranes and Interacts with the Light‐Harvesting Complex II (LHCII) of Photosystem II

Abstract

The brevetoxins are neurotoxins that are produced by the "Florida red tide" dinoflagellate Karenia brevis. They bind to and activate the voltage-gated sodium channels in higher organisms, specifically the Nav 1.4 and Nav 1.5 channel subtypes. However, the native physiological function that the brevetoxins perform for K. brevis is unknown. By using fluorescent and photoactivatable derivatives, brevetoxin was shown to localize to the chloroplast of K. brevis where it binds to the light-harvesting complex II (LHCII) and thioredoxin. The LHCII is essential to non-photochemical quenching (NPQ), whereas thioredoxins are critical to the maintenance of redox homeostasis within the chloroplast and contribute to the scavenging of reactive oxygen. A culture of K. brevis producing low levels of toxin was shown to be deficient in NPQ and produced reactive oxygen species at twice the rate of the toxic culture, implicating a role in NPQ for the brevetoxins.

Marine natural products

“…Differences between toxic and low toxicity K. brevis strains in NPQ and reactive oxygen species (ROS) production supported this. 502…”

Impact of light intensity and quality on chromatophore and nuclear gene expression in Paulinella chromatophora, an amoeba with nascent photosynthetic organelles

“…Production of ROS was measured according to a previous protocol (Cassell et al ., ), with some modifications. A 25‐ml volume of Paulinella chromatophora culture (1.9 × 10 4 cells ml −1 , 0.25 μg Chl a ml −1 ) was transferred to 50‐ml flasks, illuminated under different intensities of white (0, 15, 30, 60, 90 and 120 μmol photons m −2 sec −1 ), blue (0, 5, 10, 20 and 40 μmol photons m −2 sec −1 ) or red (0, 5, 10, 20 and 40 μmol photons m −2 sec −1 ) light for 8 h. CM‐H 2 DCFDA (a cell‐permeable ROS indicator, 50 μg per tube; Life Technologies, http://www.thermofisher.com/us/en/home.html; catalog no.…”

Brevetoxin-2, is a unique inhibitor of the C-terminal redox center of mammalian thioredoxin reductase-1

“…In gel digestion and LC-Electrospray Ionization MS/MS (LC-ESI MS/MS) analysis was performed by the Proteomics and Mass Spectrometry Facility at the UMass Medical School as previously described. 9 …”

“…Using fluorescent and photoaffinity derivatives of brevetoxin, we demonstrated that exogenously applied brevetoxin localizes to the chloroplast of K. brevis where it interacts with two chloroplast proteins including thioredoxin (Trx). 9 Trx is the parent of a family of enzymes which mediate the redox state within a cell via thiol disulfide exchange. 10 Trx is converted from its inactive disulfide form to its active dithiol through reduction by thioredoxin reductase (TrxR).…”