Models of ion pores in N-type voltage-gated calcium channels.

Two computer models of the outer vestibule of the pore of the N-type voltage-gated Ca2+ channel are predicted. The models are constructed from beta-hairpin peptide segments in the S5-S6 loops of each of the four domains that produce the channel. These hairpins together are modeled to form a short eight-stranded beta barrel. The models contain a ring of glutamates at the base of the barrel, which have been shown by mutagenesis experiments to function as a selectivity filter. These filters are suggested by the models to be of the correct dimensions to allow the permeation of a hydrated calcium ion, where the filter glutamates may substitute for molecules of water from the hydration shell of the ion. The models also suggest that a ring of threonines and an aspartate might be present between the mouth of the pore and the filter, and hence the models may prove useful in suggesting future mutagenesis experiments.