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.

[2] The proteins are typically 60-74 amino acid residues long, though some have additional N- or C-terminal extensions.

[8] Others, such as α-cobratoxin, can form both homodimers and heterodimers which have distinct pharmacological activities in vitro, though their functional significance is unclear due to their very low concentration in venom.

[10] Despite their conserved shared structure, 3FTx proteins have a wide range of pharmacological effects mediating their toxicity.

[2] Many of the most well-characterized 3FTx proteins exert their toxic effects through binding to nicotinic acetylcholine receptors (nAChRs), a family of ligand-gated ion channels.

3FTx binding interferes with cholinergic intercellular signaling particularly at neuromuscular junctions and causes paralysis.

[11][2] Alpha-bungarotoxin, the alpha-neurotoxin from the many-banded krait (Bungarus multicinctus), has a long history of use in molecular biology research; it was through the study of this toxin that nAChRs were isolated and characterized, which facilitated the study of the subunit composition of tissue-specific nAChRs and the detailed pharmacological understanding of the neuromuscular junction.

This 3FTx group is sometimes referred to as the "curaremimetic" toxins due to the similarity of their effects with the plant alkaloid curare.

[2] Another class, called the beta-cardiotoxins, causes decreased heart rate and are thought to function as beta blockers, antagonists for the beta-1 and beta-2 adrenergic receptors.

Known functional sites conferring binding affinity and specificity are concentrated in the loops of 3FTx proteins.

[21] In some 3FTx proteins with a C-terminal extension, these residues also participate in forming key binding interactions.

[28] Traditionally, this has been conceptualized as repeated events of duplication followed by neofunctionalization and recruitment to gene expression patterns restricted to venom glands.