A family of glutamate receptor genes: evidence for the formation of heteromultimeric receptors with distinct channel properties.

We have isolated two cDNA clones (GluR-K2 and GluR-K3) that share considerable sequence identity with the previously described glutamate receptor subunit, GluR-K1. The three glutamate receptor subunits show significant sequence conservation with the glutamine binding component of the glutamine permease of E. coli. Each of these clones encodes a channel responsive to both kainate and AMPA. The coexpression of GluR-K2 with either GluR-K3 or GluR-K1 results in the formation of channels whose current-voltage relationships differ from those of the individual subunits alone and more closely approximate the properties of kainate receptors in neurons. These observations indicate that the kainate/quisqualate receptors are encoded by a family of genes and are likely to be composed of hetero-oligomers of at least two distinct subunits.