Spider venom toxin that shows calcium channel blocking activity and exhibits cytolytic activity by affecting the outer leaflet curvature and/or pore formation across the membrane (PubMed:22613721, PubMed:32290562). It blocks L-type calcium channels (Cav1/CACNA1) 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 (PubMed:17517422). Potassium ions, histamine, M-ctenitoxin-Cs1a (AC P83619), CSTX-9 (AC P58604), and CSTX-13 (AC P83919) synergistically increase the insecticidal activity of this toxin (PubMed:15914655, PubMed:32290562). In vivo, it causes paralysis in blow flies and provokes death in drosophila (PubMed:32290562). Blocks voltage-activated calcium channels (Cav) (By similarity). Does not induce cell membrane permeability increase when tested on Xenopus oocytes. No alpha-helical structures are detectable. Is 7-fold less neurotoxic than omega-ctenitoxin-Cs1a on drosophila flies. Blocks voltage-activated calcium channels (Cav) (By similarity). Is 190-fold less neurotoxic than omega-ctenitoxin-Cs1a on drosophila flies. Monomer (Probable). Interacts with CSTX-13 (AC P83919) (Kd=430 nM), but does not interact with CSTX-9 (AC P58604) (PubMed:32290562). Expressed by the venom gland. The presence of a 'disulfide through disulfide knot' structurally defines this protein as a knottin. LD(50) is 0.535 pmol/mg when intrathoracically injected into drosophila. LD(50) is 0.432 pmol/mg when intrathoracically co-injected with CSTX-9 (AC P58604) into drosophila. LD(50) is 0.075 pmol/mg when intrathoracically co-injected with CSTX-13 (AC P83919) into drosophila. LD(50) is 2.58 pmol/mg on Drosophila. LD(50) is 66.51 pmol/mg on Drosophila. Omega-ctenitoxin-Cs1a is the most abundant neurotoxin in the venom of C.salei. Omega-ctenitoxin-Cs1a has no antimicrobial activity against E.coli (ATCC 25922) and S.aureus (ATCC29213). Surprisingly, it destroys the E.coli mutant (SBS363) in a concentration of 31.25 uM (PubMed:22613721). Belongs to the neurotoxin 19 (CSTX) family. 04 (U1-Lctx) subfamily.