THE LOW-MOLECULAR-WEIGHT PROTEIN WHICH COPURIFIES WITH ALPHA-LATROTOXIN IS STRUCTURALLY RELATED TO CRUSTACEAN HYPERGLYCEMIC HORMONES

LMWP is the low molecular weight protein which co-purifies with alpha- latrotoxin, the main neurotoxin from the black widow venom. It contain s 70 residues and three disulfides. We found that its primary structur e, including its 6 half cystines, can be aligned with the amino acid s equences of crustacean hyperglycemic hormones (CHHs) which contain 72- 73 residues and three disulfides. To further investigate this structur al relationship, we produced a recombinant analog of LMWP in which the unique Met was changed in Leu (LMWP(M35L)). LMWP(M35L) was produced a s a folded fusion protein in the periplasm of Escherichia coli and was generated in vitro by treating the fusion protein with cyanogen bromi de. We showed that LMWP(M35L) and CHHs have an identical disulfide pai ring pattern and possess some alpha-helical structure, as deduced from a comparison of their circular dichroism spectra. In addition, LMWP(M 35L) and CHHs are consensually predicted to possess a helical structur e within the region 13-17. Together, the data indicate that CHHs are s tructurally related to LMWP(M35L) and presumably also to LMWP. Finally , preliminary studies showed that LMWP(M35L) is not toxic to mice and does not form channels in lipid bilayers, two well-known properties of alpha-latrotoxin preparations.