38th Annual Meeting of the Society for Invertebrate Pathology

August 7-11, 2005  Anchorage, Alaska, U.S.A
   

Structural and functional analysis of the pre-pore and membrane inserted pore of Cry1A toxins.

Liliana Pardo1, Isabel Gómez1, Carlos Muñoz-Garay1, Nuria Jimenez-Juaréz1, Sarjeet S. Gill2, Mario Soberón1 and Alejandra Bravo1
1 Instituto de Biotecnología Universidad Nacional Autonoma de Mexico, Cuernavaca 62250 Mor. Mexico. 2Department of Cell Biology and Neuroscience, University of California, Riverside, CA92521, USA.

Insecticidal Cry proteins undergo conformational changes from a monomeric structure to a prepore-oligomeric form that is membrane insertion competent. We have characterized the structural and functional changes of Cry toxins upon oligomerization and membrane insertion. We studied the stability of these three structures after urea and thermal denaturation by monitoring intrinsic tryptophan fluorescence of the protein and 1-anilino naphthalene-8-sulfonic acid (ANS) binding to unfolded proteins. Our studies suggest that a more flexible conformation could be necessary for membrane insertion and this flexible structure is obtained by toxin oligomerization (Biochemistry 2004, JBC 2004). Finally we will present data regarding the interaction of the pre-pore with the second receptor (APN) by using antibodies that specifically recognize the Cry1Ab oligomeric structure and affects this interaction. Our data suggests that at least two receptor molecules, cadherin and APN, are sequentially involved in the interaction of Cry1 toxins with its target membrane.

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