Melittin, amino acid sequences

Fig. 5. (A) Amino acid sequence of melittin and a model lytic peptide. (B) Axial helical projection (Schiffer and Edmundson, 1967) of the model peptide. Taken from DeGrado et al. (1981).

Kreil, G., 1973, Biosynthesis of melittin, a toxic peptide from bee venom, amino acid sequence of the precursor. Eur. J. Biochem. 33 558-566. 

Melittin, a toxin in bee venom, is a pentacationic peptide composed of 26 amino acids. Four of the basic residues occur in a cluster near the C-terminus. The retromer made of the enantiomeric amino acids in a reversed sequence (Scheme 9.6.1) forms helices in water containing 20% hexafluoro-2-propanol as a cosolvent. The CD spectra of L-melittin and retroenantio melittin (retro d-melittin) are approximately mirror images, but both are equally effective in their antibacterial activity. The toxic action of melittin can therefore not function via a (protein) receptor or enzyme-type action. The only other possibility is formation of ion-conducting pores by self-aggregation (Juvvadi, 1997). 

Melittin a linear, toxic (hemolytic) polypeptide amide, and the chief component of bee venom (about 50 % of dried venom, and at least in 50-fold molar excess over other venom constituents). The primary product of M. biosynthesis is prepromelittin, consisting of 70 amino acid residues Removal of the N-terminal signal sequence of 21 residues (see Signal hypothesis) leaves promelittin. The protease required for removal of the signal sequence is present in many animal cells and is not species-specific, e. g. promelittin and not prepromelittin is the first detectable product when melittin mRNA is injected into oocytes of Xenopus laevis. 

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