ION CHANNELS FORMED IN PLANAR LIPID BILAYERS BY BACILLUS-THURINGIENSIS TOXINS IN THE PRESENCE OF MANDUCA-SEXTA MIDGUT RECEPTORS

A purified, GPI-linked receptor complex isolated from Manduca sexta mi dgut epithelial cells was reconstituted in planar Lipid bilayers. CryI Aa, CryIAc and CryIC, three Bacillus thuringiensis insecticidal protei ns, formed channels at much lower doses (0.33-1.7 nM) than in receptor -free membranes, The non-toxic protein CryIB also formed channels, but at doses exceeding 80 nM. The channels of CryIAc, the most potent tox in against M. sexta, rectified the passage of cations, All other toxin channels displayed linear current-voltage relationships, Therefore, r econstituted Cry receptors catalyzed channel formation in phospholipid membranes and, in two cases, were involved in altering their biophysi cal properties. (C) 1997 Federation of European Biochemical Societies.