APEKTx1

Kunitz-type serine protease inhibitor APEKTx1 is a peptide toxin derived from the sea anemone Anthopleura elegantissima.

This toxin has a dual function, acting both as a serine protease inhibitor and as a selective and potent pore blocker of Kv1.1, a shaker related voltage-gated potassium channel.

Other type 2 toxins are the kalicludines from Anemonia sulcata, which selectively block Kv1.2 channels,[5] and SHTX II from Stichodactyla haddoni.

However, trypsin inhibition is more potent (as it has a higher affinity) in BPTI, which can be explained by the presence of Phe13 and Pro19 in APEKTx1, causing an unfavorable interaction.

[1][9] APEKTx1’s dyad is formed by Arg15 and Phe13, separated by 6.2 Å, contributing to the formation of a physical barrier that opposes the K+ efflux.

APEKTx1 monomer structure prediction (Alpha-fold model). The average per residue confidence (pLDDT) is 91.46%. The levels of confidence of the model are color coded: dark blue very high (pLDDT > 90), light blue high (90 > pLDDT > 70), orange low (70 > pLDDT > 50), and yellow very low (pLDDT < 50).