Antihypertensive protein BDS-1

Blue biotechnologies implement marine bio-resources for addressing practical concerns. The isolation of biologically active molecules from marine animals is one of the main ways this field develops. Strikingly, cnidaria are considered as sustainable resources for this purpose, as they possess unique cells for attack and protection, producing an articulated cocktail of bioactive substances. The Mediterranean sea anemone Anemonia viridis has been studied extensively for years. In this short review, we summarize advances in bioprospecting of the A. viridis toxin arsenal. A. viridis RNA datasets and toxin data mining approaches are briefly described. Analysis reveals the major pool of neurotoxins of A. viridis, which are particularly active on sodium and potassium channels. This review therefore integrates progress in both RNA-Seq based and biochemical-based bioprospecting of A. viridis toxins for biotechnological exploitation.

Sea anemone venom is known to contain toxins that are active on voltage-sensitive Na+ channels, as well as on delayed rectifier K+ channels belonging to the Kv1 family. This report describes the properties of a new set of peptides from Anemonia sulcata that act as blockers of a specific member of the Kv3 potassium channel family. These toxins, blood depressing substance (BDS)-I and BDS-II, are 43 amino acids long and differ at only two positions. They share no sequence homologies with other K+ channel toxins from sea anemones, such as AsKS, AsKC, ShK, or BgK. In COS-transfected cells, the Kv3.4 current was inhibited in a reversible manner by BDS-I, with an IC50 value of 47 nM. This inhibition is specific because BDS-I failed to block other K+ channels in the Kv1, Kv2, Kv3, and Kv4 subfamilies. Inward rectifier K+ channels are also insensitive to BDS-I. BDS-I and BDS-II share the same binding site on brain synaptic membranes, with K0.5 values of 12 and 19 nM, respectively. We observed that BDS-I and BDS-II have some sequence homologies with other sea anemone Na+ channels toxins, such as AsI, AsII, and AxI. However, they had a weak effect on tetrodotoxin-sensitive Na+ channels in neuroblastoma cells and no effect on Na+ channels in cardiac and skeletal muscle cells. BDS-I and BDS-II are the first specific blockers identified so far for the rapidly inactivating Kv3.4 channel.

The crude extracts from three species of sea anemones (Cryptodendrum adhaesivum, Heterodactyla hemprichii and Thalassianthus aster) belonging to the family Thalassianthidae exhibited potent lethality to freshwater crabs (Potamon dehaani). Regardless of the species, high and low molecular weight toxins were found in gel filtration of the crude extract. Following reverse-phase HPLC of the low molecular weight toxin fractions, one toxin (δ-TLTX-Ca1a), two toxins (δ-TLTX-Hh1a and c) and one toxin (δ-TLTX-Ta1a) were isolated from C. adhaesivum, H. hemprichii and T. aster, respectively. Based on the determined N-terminal amino acid sequences, the cDNAs encoding δ-TLTX-Ca1a, δ-TLTX-Hh1x (not assignable to either δ-TLTX-Hh1a or δ-TLTX-Hh1c) and δ-TLTX-Ta1a were successfully cloned by both 3' and 5' RACE methods. In common with the three toxins, the precursor is composed of a signal peptide (19 amino acid residues), propart (16 residues) and mature portion (49 residues), similar to those of many sea anemone peptide toxins. The deduced amino acid sequences showed that the three toxins are closely similar to one another, being all new members of the type 2 sea anemone sodium channel peptide toxin family.