An Overview of The Three Dimensional Structure of Short Spider Toxins

Abstract

Arthropods are one of the most diverse animal groups on the Earth. Spiders belong to this phylum and they are ancient animals with a history going back some three hundred million years. They are abundant, widespread, and natural controllers of insect populations. They use their venom to capture prey or to fight against predators. This venom is constituted of various peptides and enzymes with different activities. Among these proteins, toxic peptides are responsible for the macroscopic effect of the venom.

Most of the toxins are known to interact with ion channels (mainly potassium channels, sodium channels, and calcium channels). These transmembrane molecules are ubiquitous in the cells. They underlie a broad range of the most basic biological processes, from excitation and signaling to secretion and absorption. Like enzymes they are diverse and ubiquitous macromolecular catalysts with high substrate specificity and subject to strong regulation. Animal toxins and, more specifically, spider toxins are effectors of these channels. Depending on the peptide, they have ability to block the channel by plugging into its pore of conduction, or by modifying the opening and closing capacity of the channels, binding on a few specific sites along the structure of the channel.

Most of these peptides fold according to the overall same pattern, the inhibitor cystine knot (ICK) scaffold. Basically, it consists of a ring formed by a part of the backbone of the peptide and two disulfide bridges, penetrated by a third disulfide bridge. An additional disulfide bridge might be found in some toxins. Another fold has been found in a few toxins and has been described as the DDH scaffold. This motif lacks the knot and comprises an antiparallel β -hairpin stabilized by two conserved disulfide bridges.

This paper will try to summarize the structural characteristics of the spider toxins for which the fold has been described in the literature.

Keywords:

• Spiders
• Spider toxins
• Structure determination
• Ion channels
• ICK structural motif.