Channels formed by M2 peptides of a putative glutamate receptor subunit of locust

A cDNA encoding part of a polypeptide (Loc1) that exhibits similarity to the corresponding portion of the rat GluR1 subunit has been identified by screening an amplified locust cDNA library. This polypeptide is deduced to be missing about 200 amino acids of the amino-terminus and about 100 amino acids of the carboxy-terminus. cDNAs encoding two other glutamate receptor-like polypeptides (Loc2 and Loc3), which both exhibit good sequence homology with Loc1, have also been identified. So far, there is no evidence for 'flip' and 'flop' variants of Loc1, 2 and 3. A 27-mer peptide including the M1 sequence of Loc1 and a 25-mer peptide including the M2 sequence of this putative glutamate receptor subunit have been synthesised and incorporated into artificial bilayers. Channel openings, of minimum conductance 20 pS, were seen more frequently with the M2 peptide. These studies are designed to lead to the isolation of full-length cDNAs for Loc1, 2 and 3 and to the electrophysiological characterisation of their ion transport properties.