Ts 19 Frag-II is a new toxin isolated from Tityus serrulatus venom with 5534 Da.

Ts19 Frag-II is a β-KTx class (subfamily) 2 toxin and presents a selective and significant blocking effect on Kv1.2 channel.

We speculate that Ts19 Frag-I should be the precursor toxin, which originates Ts19 Frag-II and III.

Ts19 Frag-III showed to be cytolytic and did not block the Kv1.2 channel.

A new post-translational toxin modification is discussed: post-splitting.