UNRAVELING THE MODULAR DESIGN OF GLUTAMATE-GATED ION CHANNELS

Glutamate receptors that function as ligand-gated ion channels are ess ential components of cell-cell communication in the nervous system. De spite a wealth of information concerning these receptors, details of t heir structure are just beginning to emerge. We propose that glutamate receptors comprise four modules: two modules that are related to bact erial periplasmic-binding proteins, one module that is related to the pore-forming region of K+ channels, and one regulatory module of unkno wn origin. A K+-channel-like domain inserted into a crucial region of a periplasmic-binding protein-like domain suggests a mechanism for tra nsduction of binding energy to channel opening. This modular design al so suggests an evolutionary link between a ligand-gated ion-channel fa mily and voltage-gated ion channels.