8.B.19.2.2
Peptide toxin, Cs1a omega ctenitoxin, of 122 aas from a spider multicomponent venom.  It contains a cystine knot structure and is therefore called a knottin (Kuhn-Nentwig et al. 2012). Double-knottin peptides from spider venom have been used to reveal aspects of the pharmacology of transmembrane channels (Agwa et al. 2018). It shows calcium channel blocking activity and exhibits cytolytic activity by affecting the outer leaflet curvature and/or pore formation across the membrane (Kuhn-Nentwig et al. 2012, Clémençon et al. 2020). It blocks L-type calcium channels (Cav1/CACNA1) (TC# 1.A.1.11.4) in mammalian neurons at nanomolar concentrations. Furthermore, it produces a slow voltage-independent block of mid/low and high voltage-activated calcium channels in cockroach neurons (Kubista et al. 2007). Potassium ions, histamine, M-ctenitoxin-Cs1a (P83619), CSTX-9 (P58604), and CSTX-13 (P83919) synergistically increase the insecticidal activity of this toxin (Wullschleger et al. 2005, Clémençon et al. 2020). In vivo, it causes paralysis in blow flies and provokes death in Drosophila (Clémençon et al. 2020).