Cloning and functional expression of novel N-type Ca2+ channel variants

Voltage-dependent Ca2+ channels are structurally and functionally diverse. As Ca2+ currents recorded from embryonic chick dorsal root ganglion (DRG) n eurons differ significantly from their mammalian counterparts, information on the primary sequence of the chick channels will help define the structur al underpinnings of Ca2+ channel function. Here, we report the cloning and functional expression of full-length Ca2+ channel alpha(1B) subunit cDNAs d erived from chick DRGs. Two variable regions (A and B) have been identified in the cytoplasmic linker between repeats I and II; a third (C) in the car boxyl terminus extends the open reading frame by 525 nucleotides. The A and C inserts are absent, and the B insert is present in all other class B clo nes reported to date. The unique shorter channels appear to predominate in DRG neurons. Results represent a requisite first step in defining the struc tural elements that underlie variations in function and modulation of Ca2channels.