Acetylcholine receptor inhibiting toxin ~ VenomZone

Channel

Nicotinic acetylcholine receptors (nAChR) are postsynaptic membrane proteins that undergo an extensive conformational change upon binding to acetylcholine, leading to opening of an ion-conducting channel across the plasma membrane.

Nicotinic receptors, with a molecular mass of 290 kDa, are made up of five subunits, arranged symmetrically around a central pore. Each subunit comprises four transmembrane domains with both the N- and C-terminus located extracellularly.

In vertebrates, nicotinic receptors are broadly classified into two subtypes based on their primary sites of expression: muscle-type nicotinic receptors and neuronal-type nicotinic receptors.

Figure 1: Schematic representation of the fetal muscle subtype nAChR (a) and the adult muscle subtype nAChR (b).

In the muscle-type receptors, found at the neuromuscular junction, receptors are either the embryonic form, composed of α1, β1, δ and γ subunits in a 2:1:1:1 ratio (Fig.1a), or the adult form composed of α1, β1, δ and ε subunits in a 2:1:1:1 ratio (Fig.1b). The neuronal subtypes are various homomeric or heteromeric combinations of twelve different nicotinic receptor subunits: α2 through α10 and β2 through β4. Examples of the neuronal subtypes include: (α4)3(β2)2, (α4)2(β2)3 and (α7)5. In both muscle-type and neuronal-type receptors the subunits are somewhat similar to one another, especially in the hydrophobic regions.

Toxin

	Channel Receptor	Toxins from different taxa that target channels/receptors. Click on to retrieve toxins of interest.
	Human	Snake	Scorpion	Cone snail	Spider	Cnidarian	Insect	Other	All
Muscle AChR
α1β1δε (adult) CHRNA1-CHRNB1-CHRND-CHRNE			-		-	-	-	-
α1β1γδ (fetal) CHRNA1-CHRNB1-CHRNG-CHRND			-		-	-	-	-

Neuronal AChR
α2β2 / CHRNA2-CHRNB2		-	-		-	-	-	-
α2β4 / CHRNA2-CHRNB4		-	-		-	-	-	-
α3β2 / CHRNA3-CHRNB2			-		-	-	-	-
α3β4 / CHRNA3-CHRNB4		-	-		-	-	-	-
α4β2 / CHRNA4-CHRNB2			-		-	-	-	-
α4β4 / CHRNA4-CHRNB4		-	-		-	-	-	-
α6β4 / CHRNA6-CHRNB4		-	-		-	-	-	-
α6/α3β2 ¹ CHRNA6/CHRNA3-CHRNB2		-	-		-	-	-	-
α6/α3β2β3 ¹ CHRNA6/CHRNA3-CHRNB2-CHRNB3		-	-		-	-	-	-
α6/α3β4 ¹ CHRNA6/CHRNA3-CHRNB4		-	-		-	-	-	-
α7 / CHRNA7			-		-	-	-	-
α9α10 / CHRNA9-CHRNA10		-	-		-	-	-	-
All			-		-	-	-	-

¹ : The α6/α3 subunit is a chimera containing the N-terminal extracellular ligand-binding portion of the α6 subunit with the remaining α3 subunit (Kuryatov et al., 2000).

Acetylcholine receptor inhibiting toxin (nAChR inhibitor)

Venom protein entries in UniProtKB/Swiss-Prot

Conotoxin A superfamily

Conotoxin B superfamily

Conotoxin D superfamily

Conotoxin J superfamily

Conotoxin L superfamily

Conotoxin M superfamily

Conotoxin O1 superfamily

Conotoxin S superfamily

FARP (FMRFamide related peptide) family

Not in a family

Phospholipase A2 family, Group I subfamily, D49 sub-subfamily

Phospholipase A2 family, Group II subfamily, D49 sub-subfamily

Phospholipase A2 family, Group II subfamily, S49 sub-subfamily

Sea anemone type 3 (BDS) potassium channel toxin family

Short scorpion toxin superfamily, Potassium channel inhibitor kappa-KTx family, Kappa-KTx 5 subfamily

Snake three-finger toxin family, Ancestral subfamily

Snake three-finger toxin family, Ancestral subfamily, Boigatoxin sub-subfamily

Snake three-finger toxin family, Ancestral subfamily, Orphan group II sub-subfamily

Snake three-finger toxin family, Ancestral subfamily, Orphan group IV sub-subfamily

Snake three-finger toxin family, Ancestral subfamily, Orphan group XVII sub-subfamily

Snake three-finger toxin family, Long-chain subfamily, Kappa-neurotoxin sub-subfamily

Snake three-finger toxin family, Long-chain subfamily, Type II alpha-neurotoxin sub-subfamily

Snake three-finger toxin family, Short-chain subfamily

Snake three-finger toxin family, Short-chain subfamily, Orphan group VIII (haditoxin) sub-subfamily

Snake three-finger toxin family, Short-chain subfamily, Type I alpha-neurotoxin sub-subfamily

Snake three-finger toxin family, Short-chain subfamily, Type III alpha-neurotoxin sub-subfamily

Waglerin family