Functional and structural study comparing the C-terminal amidated β-neurotoxin Ts1 with its isoform Ts1-G isolated from Tityus serrulatus venom

Abstract

Mature Ts1, the main neurotoxin from Tityus serrulatus venom, has its C-terminal Cys amidated, while the isolated isoform of Ts1, named Ts1-G, keeps the non-amidated Gly residue at the C-terminal region, allowing the study of the comparative functional importance of amidation at the C-terminal between these two native toxins. Voltage dependent sodium current measurements showed that the affinity of Ts1-G for sodium channels is smaller than that of the mature Ts1, confirming the important role played by the C-terminal amidation in determining Ts1 activity.

The Scorpion Toxin Tf2 from Tityus fasciolatus Promotes Nav1.3 Opening

“…The nucleotide sequence that codes for Tf2 contains 255 nucleotides, including the stop codon, and the translated peptide contains a signal peptide with 20 amino acid residues, and a 62 residue mature peptide (Fig 2A). Na v channel scorpion toxins containing a GK at the C-terminal end are frequently amidated [40], an important feature for toxins such as Ts1 and CssII since this post translational modification increases their biological activity [41,42]. Taking protein amidation into account (-0.98 Da), as well as the presence of four disulfide bridges, the theoretical monoisotopic molecular mass is [M+H] + 6,950.0302 Da, which corresponds with the experimental monoisotopic molecular mass of [M+H] + 6,949.9350 Da (or [M+7H] 7+ = 993.7050) obtained by using the micrOTOF QII (see inset Fig 1A).…”

Subtype Specificity of β-Toxin Tf1a from Tityus fasciolatus in Voltage Gated Sodium Channels

“…The translated peptide is composed of 81 amino acids residues, of which the first 20 amino acid residues are the signal peptide and the remaining 61 residues is the mature peptide ( Figure 2 ). The sequence also shows the presence of GKK in the C-terminal, which is an amidation signal present in several scorpion sodium toxins (NaScTxs), and in some cases, such as in the toxin Ts1 from Tityus serrulatus , C-terminal amidation is important for NaScTx activity on sodium channels [ 9 , 21 ].…”

Recombinant production and structure-function study of ts1 toxin from the Brazilian scorpion Tityus serrulatus

“…1б), и его 15 N-меченого аналога. Вариант токсина с Gly62 присутствует в природном яде наряду с основным компонентом, содержащим карбоксиамидную группу на C-конце (Cys61-CONH 2 ) [12].…”

“…3а, в). Рекомбинантный Ts1 обладал меньшей активностью по сравнению с природным токсином [8], что ранее наблюдалось для природных и синтетических аналогов Ts1, не содержащих, как и в настоящей работе, C-концевую карбоксиамидную группу [11,12]. Токсин сдвигал кривую зависимости активации канала Na V 1.4 в сторону более отрицательных значений мембранного потенциала (облегчал активацию канала), что характерно для β-токсинов скорпионов, действующих на сайт 4 (рис.…”