Spider Venom

Chemistry of Spider Venom

NeuronThe majority of spiders possess neurotoxic venom.  These neurotoxins are multicomponent but contain three main groups of toxic compounds:

Other venom components include inorganic ions and salts, free acids (eg. lactic acid), glucose, nucleic acids, free amino acids and biogenic amines.  The exact role of these is unknown but they are thought to aid the stability, delivery and effectiveness of the toxins.Synapse

The excitability of the cell membrane and the transmission of electrical signals across a synapse are very important in the function nerve tissue.  As a result, neuronal receptors, ion channels or membrane proteins involved in neurotransmitter release are attacked by most venoms.

Picture from reference 12


The structure of a spider polyamine consists of a hydrophobic, aromatic carboxylic acid region connected to a hydrophilic polyamine amide chain.

General structure of a spider polyamine

Polyamines work by blocking neuromuscular junctions in insects to prevent the release of the main neurotransmitter, glutamate, resulting in paralysis.  These toxins tend to be specific for insects and not vertebrates.


These attack ion channels and are the major components of spider toxins.  Ion channels are proteins situated on the nerve cell membrane, through which ions can pass to move across the membrane.  The channels control the electrical potential of the membrane and ionic balance so they are vital in neurotransmitter release.  The different types of ion channel and examples of the toxins which affect them are discussed below.

Polypeptide toxins all have the same basic structure.  A single polypeptide molecule is folded so that a b-sheet consisting of three strands is made.  The overall structure of the peptide is termed a ‘cysteine knot’.

Images from reference 8        Structures of polypeptide toxins and schematic diagram of a cysteine knot


An example of a neurotoxic protein is a-latrotoxin from the black widow spider.  It is highly toxic to vertebrates and causes massive neurotransmitter release.

Enzyme proteins are used in necrotoxins.  The active enzyme in brown recluse spider venom is sphingomyelinase D which causes the degradation of cell membranes and the development of painful lesions.