Latisemin is a cysteine-rich secretory protein that can be isolated from the venom of the Black-banded sea krait, a sea snake indigenous to the warmer waters of the western Pacific Ocean. It is a toxin that inhibits cyclic nucleotide-gated ion channels [1] and blocks L-type calcium channels, thereby reducing smooth muscle contraction. [2]
Latisemin is a component of the venom produced by the Erabu sea snake ( Laticauda semifasciata ) of the family Elapidae and the Laticauda genus. These sea snakes inhabit coral reef areas in the seas of Southern Japan, Southeast Asia, and Australia. [2] Though highly venomous, this snake is comparatively unaggressive, and is in fact caught and eaten in Erabu soup in Japan.
Latisemin has a molecular weight of 24 kDa and consists of 217 amino acids. [1] [3] It belongs to the CRISP (cysteine-rich secretory protein) glycoprotein subfamily, [4] which are single chain polypeptides containing strictly conserved cysteines [1] (cysteines not oxidised to cystine and thus not providing disulfide bond support to tertiary protein structure). They are secretory proteins, meaning they are secreted from cells into extracellular fluid.
Latisemin strongly blocks depolarization- (but not caffeine-) induced smooth muscle contraction, [2] suggesting that it blocks L-type calcium channels. Its mode of action is similar to that of some other snake venom toxins from the CRISP family, like ablomin from the Japanese Mamushi snake and triflin from the Habu snake. [2] They also inhibit cyclic nucleotide-gated ion channels. [1]
Other snake venom proteins in the CRISP family:
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved venom apparatus, such as fangs or a stinger, in a process called envenomation. Venom is often distinguished from poison, which is a toxin that is passively delivered by being ingested, inhaled, or absorbed through the skin, and toxungen, which is actively transferred to the external surface of another animal via a physical delivery mechanism.
Snake venom is a highly toxic saliva containing zootoxins that facilitates in the immobilization and digestion of prey. This also provides defense against threats. Snake venom is usually injected by unique fangs during a bite, though some species are also able to spit venom.
A conotoxin is one of a group of neurotoxic peptides isolated from the venom of the marine cone snail, genus Conus.
Ophanin is a toxin found in the venom of the King Cobra, which lives throughout South East Asia. This toxin belongs to the cysteine-rich secretory protein (CRISP) family. Ophanin weakly blocks the contraction of smooth muscles elicited by high potassium-induced depolarization, suggesting that it inhibits voltage-dependent calcium channels.
The Indian cobra, also known commonly as the spectacled cobra, Asian cobra, or binocellate cobra, is a species of cobra, a venomous snake in the family Elapidae. The species is native to the Indian subcontinent, and is a member of the "big four" species that are responsible for the most snakebite cases in India.
Gloydius blomhoffii, commonly known as the mamushi, Japanese moccasin, Japanese pit viper, Qichun snake, Salmusa or Japanese mamushi, is a pit viper species found in Japan. It was once considered to have 4 subspecies, but it is now considered monotypic.
Calciseptine (CaS) is a natural neurotoxin isolated from the black mamba Dendroaspis p. polylepis venom. This toxin consists of 60 amino acids with four disulfide bonds. Calciseptine specifically blocks L-type calcium channels, but not other voltage-dependent Ca2+ channels such as N-type and T-type channels.
Crotamine is a toxin present in the venom of the South American rattlesnake. It is a 42-residue-long protein containing 11 basic residues and six cysteines. It has also been isolated from the venom of North American prairie rattlesnake, Crotalus viridis viridis. It was first isolated and purified by Brazilian scientist José Moura Gonçalves, and later intensively studied by his group of collaborators at the Medical School of Ribeirão Preto of the University of São Paulo.
The black-banded sea krait, also known commonly as the Chinese sea snake or erabu, is a largely amphibious species of venomous marine reptile in the subfamily Laticaudinae, family Elapidae. It is found in much of the western Pacific Ocean and some of the Sea of Japan. In Japan, it is known as erabu umi hebi ; in Okinawa, it is known simply as irabu.
Cysteine-rich secretory protein 3 is a cysteine-rich secretory protein that in humans is encoded by the CRISP3 gene.
Cysteine-rich secretory protein 2 is a cysteine-rich secretory protein that in humans is encoded by the CRISP2 gene.
Ablomin is a toxin present in the venom of the Japanese Mamushi snake, which blocks L-type voltage-gated calcium channels.
Triflin is a cysteine-rich secretory protein (CRISP), which is excreted by the venom gland of the Habu snake. Triflin reduces high potassium-induced smooth muscle contraction, suggesting a blocking effect on L-type calcium channels.
Piscivorin is a component of snake venom secreted by the Eastern Cottonmouth. It is a member of the cysteine-rich secretory protein (CRISP) family, which blocks voltage-dependent calcium channels.
Cysteine-rich secretory proteins, often abbreviated as CRISPs, are a group of glycoproteins. They are a subgroup of the CRISP, antigen 5 and Pr-1 (CAP) protein superfamily and also contain a domain related to the ShK toxins. They are substantially implicated in the functioning of the mammalian reproductive system. CRISPs are also found in a variety of snake venoms where they inhibit both smooth muscle contraction and cyclic nucleotide-gated ion channels.
The CAP superfamily is a large superfamily of secreted proteins that are produced by a wide range of organisms, including prokaryotes and non-vertebrate eukaryotes.
α-Neurotoxins are a group of neurotoxic peptides found in the venom of snakes in the families Elapidae and Hydrophiidae. They can cause paralysis, respiratory failure, and death. Members of the three-finger toxin protein family, they are antagonists of post-synaptic nicotinic acetylcholine receptors (nAChRs) in the neuromuscular synapse that bind competitively and irreversibly, preventing synaptic acetylcholine (ACh) from opening the ion channel. Over 100 α-neurotoxins have been identified and sequenced.
Huwentoxins (HWTX) are a group of neurotoxic peptides found in the venom of the Chinese bird spider Haplopelma schmidti. The species was formerly known as Haplopelma huwenum, Ornithoctonus huwena and Selenocosmia huwena. While structural similarity can be found among several of these toxins, HWTX as a group possess high functional diversity.
Three-finger toxins are a protein superfamily of small toxin proteins found in the venom of snakes. Three-finger toxins are in turn members of a larger superfamily of three-finger protein domains which includes non-toxic proteins that share a similar protein fold. The group is named for its common structure consisting of three beta strand loops connected to a central core containing four conserved disulfide bonds. The 3FP protein domain has no enzymatic activity and is typically between 60-74 amino acid residues long. Despite their conserved structure, three-finger toxin proteins have a wide range of pharmacological effects. Most members of the family are neurotoxins that act on cholinergic intercellular signaling; the alpha-neurotoxin family interacts with muscle nicotinic acetylcholine receptors (nAChRs), the kappa-bungarotoxin family with neuronal nAChRs, and muscarinic toxins with muscarinic acetylcholine receptors (mAChRs).
Dc1a is a potent insect-selective poisonous 57-residue peptide that is produced by the desert bush spider (Diguetia canities). It promotes the opening of voltage-gated Na channels (Nav) in German cockroach (Blattella germanica) by interacting with the paddle motif in domain II.