ABSTRACT
The family of glutamate receptor subunits is encoded by at least 17 genes in mammals. The subunits can, based on sequence comparison, be divided into seven groups with amino acid identities higher than 60 per cent within the groups and less than 40 per cent identity between the groups (Figure 2.1). The division correlates with the binding affinities determined for the three key compounds; AMPA, kainate and NMDA, which most commonly have been used to characterize the receptors in vivo. The AMPA receptors are formed from the subunits GluR1-GluR4 (also called GluRA-GluRD). The AMPA receptor subunits do not form receptor complexes with subunits from the other groups (Partin et al., 1993; Puchalski et al., 1994). The kainate receptors can be formed of members from two groups: the low affinity kainate receptor subunits, GluR5-GluR7, and the high affinity kainate receptor subunits, KA1 and KA2. The
Figure 2.1 Phylogenetic diagram based on amino acid identities.
