Tityustoxin peptide 2 (TsPep2) is a peptide isolated from the venom of the Tityus serrulatus (Brazilian yellow scorpion). It belongs to a class of short peptides, together with Tityustoxin peptide 1 and Tityustoxin peptide 3.[1]
| Infobox TsPep2 | |
| Tityustoxin peptide 2 | |
| Headerstyle: | background:#ccf; |
| Labelstyle: | background:#ddf; |
| Header1: | SCOP classification[2] |
| Label2: | Class |
| Data2: | Small proteins |
| Label3: | Superfamily |
| Data3: | Scorpion toxin-like |
| Label4: | Family |
| Data4: | Short-chain scorpion toxin[3] |
| Label5: | Species |
| Data5: | Tityus serrulatus |
| Label6: | UniProt |
| Data6: | P0C175[4] |
Tityus serrulatus, also known as the Brazilian yellow scorpion, is from the genus Tityus belonging to the family Buthidae.
TsPep2 is identified from the venom of Tityus serrulatus by using a cDNA primer sequence based on the C-terminal amino acid sequence of KTx2 from Androctonus australis.[5]
The original encoded sequence of TsPep2 consists of 68 amino acids processed in a mature peptide of 29 amino acids with a final molecular weight of 2993.59 Da.[6] TsPep2 differs in the mature sequence from TsPep3 only in one amino acid and TsPep1 shows 58,6% of sequence homology with Tspep2 and TsPep3.
| 10 | 20 | 30 | 40 | 50 | 60 | |
| MKFSCGFLLI | FLVLSAMIAT | FSEVEATVK | GGNRKAG | GRSGKING | KQYGRSDL NEEFENYQ |
Eight cysteines establish four disulfide bridges and a C-terminal tyrosine amide is present in the 55th position.Furthermore, TsPep2 sequence alignment shows that a part of the amino acid consensus sequence (CXXXKCCXC) involved in the pore blocking mechanism is present as in other known short scorpion toxins.[7]
It seems likely that TsPep2 has inhibitory actions on potassium channels, based on its sequence similarities in the C-terminal beta sheet with the potassium channel inhibitory alpha family (α-KTX) and on its similarities in the patterns of disulfide bridges with other short scorpion venom toxins.[6] [8]
The biological function of TsPep2 is not clear yet, except from a small displacement on the 125I-KTX binding site on rat brain synaptosomes.[8] However, it has been shown that this peptide is not toxic to mice.[4] The LD50 of TsPep2 is currently unknown.