... argues against a role for a3intheformation of native MII binding sites, but may reflect the scarcity of these sites in the investigated brain tissues and/or the formation of low affinity binding sites ... microdomains within the same bindingsite [35]. The proline residue in position 6, which isconserved in all other a-conotoxins, appears to be the major determinant of the abilities of ImI and ... studies. The highselectivity of the a-conotoxins, together with the possibility of obtaining detailed information on their three dimen-sional structures and the relative ease of synthesis, makesthem...