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 v oltage-gated Ca2+ channel are predicted. The models are constructed fr om beta-hairpin peptide segments in the S5-S6 loops of each of the fou r domains that produce the channel. These hairpins together are modele d to form a short eight-stranded beta barrel. The models contain a rin g of glutamates at the base of the barrel, which have been shown by mu tagenesis experiments to function as a selectivity fil ter. These filt ers are suggested by the models to be of the correct dimensions to all ow the permeation of a hydrated calcium ion, where the filter glutamat es may substitute for molecules of water from the hydration shell of t he ion. The models also suggest that a ring of threonines and an aspar tate might be present between the mouth of the pore and the filter, an d hence the models may prove useful in suggesting future mutagenesis e xperiments.