Ion permeability and single channel conductance are determined primarily by the M2 pore forming domain of ionotropic glutamate receptors. In mammals the codon for a conserved glutamine(Q) residue in M2 of the GluR-B subunit is edited so that it encodes arginine(R), limiting the conductance and permeability of AMPA channels containing it. In C. elegans no such editing has been found for the four glr genes containing this conserved domain with the Q residue, glr- 1(C06E1),
glr-2 (B0280.12), glr(ZC196.7) and glr(K10D3.1).