INSERTION OF A SNS-SPECIFIC TETRAPEPTIDE IN S3-S4 LINKER OF D4 ACCELERATES RECOVERY FROM INACTIVATION OF SKELETAL-MUSCLE VOLTAGE-GATED NA CHANNEL MU-1 IN HEK293 CELLS

Na channel subunits alpha SNS (PN3) and alpha mu 1(SkM1) produce slowl y inactivating/TTX-resistant and rapidly inactivating/TTX-sensitive cu rrents, respectively, alpha SNS (PN3) current recovers from inactivati on (reprimes) rapidly. Sequence alignment identified the tetrapeptide SLEN, in the S3-S4 linker of D4, as alpha SNS-specific. To determine w hether SLEN endows Na channels with slow kinetics and/or rapid reprimi ng, we analyzed the transient Na current produced by a chimera mu 1SLE N in HEK293 cells, Neither kinetics nor voltage dependence of activati on and inactivation was affected. However, repriming was twice as fast as in the wild type at -100 mV. This suggests that SLEN may contribut e to the rapid repriming of TTX-resistant Na current. (C) 1997 Federat ion of European Biochemical Societies.