Another large subfamily of 3FTx proteins is the cardiotoxins (also known as cytotoxins or cytolysins); this group is directly cytotoxic most likely due to interactions with phospholipids and possibly other components of the cell membrane.

[4][12] Many LU domain containing proteins are involved in cholinergic signaling and bind acetylcholine receptors, notably linking their function to a common mechanism of 3FTx toxicity.

[13] Snake three-finger toxins and the Ly6/uPAR family members share a common gene structure, typically consisting of two introns and three exons.

[4] The third exon contains the major differentiating features between the two groups, as this is where the C-terminal GPI-anchor peptide common among the Ly6/uPAR globular proteins is encoded.

[14][15] 3FTx toxins are considered restricted to the Caenophidia, the taxon containing all venomous snakes; however at least one homolog has been identified in the Burmese python, a closely related subgroup.