The electronic structure of the peptidic BgK toxin is obtained at an ab initio level with the total energy pseudopotential method using a plane wave basis expansion. A detailed analysis of the electronic structure reveals the existence of electronic unoccupied states in structural cavities generated by the particular folding of the polypeptide. The existence of such kind of electronic states is verified using different structural models of the system and employing different levels of theory. Finally, the stability upon occupation of this kind of states is determined as well as the influence of polar solvents.