Nine novel precursors of Buthus martensii scorpion alpha-toxin homologues

The cDNAs encoding nine novel alpha-toxin homologues were isolated from the venom gland cDNA library of the Chinese scorpion Buthus martensii Karsch ( BmK). They are rich in AAAA and TTTT elements at the 5' UTRs. The flanking region of the translation initiation codon ATG is AAAATGAA, which is highly conserved in scorpion Na+, K+ and Cl- channel toxin genes. These putative scorpion alpha-toxins shared 45.5-98.4% homology with the characterized BmK alpha-toxins; and were completely conserved in the positions of all eight cysteines. This showed, together with higher homology at nucleotide level t han that at amino acid level, that these toxins may originate from a common ancestor. The discovery of a series of homologues of scorpion alpha-toxin with a different degree of natural mutation in the primary structure will p rovide us with a valuable system for studying the structure-function relati onship of scorpion toxins, (C) 2000 Elsevier Science Ltd. All rights reserv ed.