Identical N-terminal peptide sequences of asymmetric forms and of low-salt-soluble and detergent-soluble amphiphilic dimers of Torpedo acetylcholinesterase : Comparison with bovine acetylcholinesterase

Abstract

We have determined partial N-terminal sequences of acetylcholinesterase (AChE) catalytic subnunits from Torpedomarmorata electric organs and from bovine caudate nucleus. We obtain identical sequences (23 amino acids) for the soluble (‘low-salt-soluble’ or LSS fraction) and particulate (‘detergent-soluble’, or DS fraction) amphiphilic dimers (G 2 form) and for the asymmetric, collagen-tailed forms (‘high-salt-soluble’, or HSS fraction, A 12 + A 8 forms). There are two amino acid differences, at position 3 (Asp/His) and 20 (Ile/Val), with the sequences obtained for T. californica by MacPhee-Quigley et al. [(1985) J. Biol. Chem. 260, 12185-12189] for the soluble G 2 form and the lytic G 4 form which is derived from asymmetric AChE. The bovine sequence (12 amino acids) presents an identity of 4 amino acids (Glu-Leu-Leu-Val) with that of Torpedo, at positions 5–8 ( Torpedo) and 7–10 (bovine). There is also a clear homology with the sequence of human butyrylcholinesterase [(1986) Lockridge et al. J. Biol. Chem., in press] indicating that these enzymes probably derive from a common ancestor.