α-Cobratoxin is a neurotoxin from the venom of certain Naja genus, including the Thailand cobra, the Indo-Chinese spitting cobra (Naja siamensis) and the Chinese cobra (Naja atra). The cobras that produce the toxin live in tropical and subtropical regions of Africa and Asia. The venom, produced by these snakes, is a mixture of proteins, carbohydrates, and other substances. The venom is only used when the snake needs it for survival, because it costs a lot of effort to produce. If poisoning a subject is not necessary, it can bite without excreting the venom. When the snake does use it, it mostly tries to immobilize or kill its prey. α-Cobratoxin forms three hairpin type loops with its polypeptide chain. The two minor loops are loop I (amino acids 1–17) and loop III (amino acids 43–57). Loop II (amino acids 18–42) is the major one. Following these loops, α-cobratoxin has a tail (amino acids 58–71). The loops are knotted together by four disulfide bonds (Cys3-Cys20, Cys14-Cys41, Cys45-Cys56, and Cys57-Cys62). Loop II contains another disulfide bridge at the lower tip (Cys26-Cys30). Stabilization of the major loop occurs through β-sheet formation. The β-sheet structure extends to amino acids 53-57 of loop III. Here it forms a triple-stranded, antiparallel β-sheet. This β-sheet has an overall right-handed twist6. This β-sheet consists of eight hydrogen bonds. The folded tip is held stable by two α-helical and two β-turn hydrogen bonds. Here you can see a crystal structure of this toxin in its dimeric form (PDB code: 4AEA)
#molecularart ... #immolecular ... #toxin ... #cobra ... #venom ... #disulfide ... #dimer ... #xray
Structure of the cobra toxin rendered with @proteinimaging and depicted with @corelphotopaint
#molecularart ... #immolecular ... #toxin ... #cobra ... #venom ... #disulfide ... #dimer ... #xray
Structure of the cobra toxin rendered with @proteinimaging and depicted with @corelphotopaint
