AMINO-ACID-SEQUENCE OF A PUTATIVE SODIUM-CHANNEL EXPRESSED IN THE GIANT-AXON OF THE SQUID LOLIGO-OPALESCENS

A full-length cDNA encoding a putative Na+ channel (GFLN1) has been cl oned from a library prepared from the stellate ganglion of Loligo opak scens. The cDNA encodes a predicted protein of 1784 amino adds. Region s of the GFLN1 protein with defined functional importance (membrane sp an S4, the SS1 and SS2 segments, and interdomain III-IV) are highly co nserved among all vertebrate Na+ channel alpha-subunit structures. Nor thern blot hybridization and RNase protection assays verify that mRNA corresponding to GFLN1 is expressed in neurons of the giant fiber lobe that form the giant axon. We propose that GFLN1 encodes the Na+ chann el that has been extensively studied in the squid axon.