Insecticidal delta-endotoxin Cyt2Ba from Bacillus thuringiensis

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Cyt2Ba, resolution 1.8Å
Gene:	cyt2Ba
Coordinates:	save as pdb, mmCIF, xml

The Cyt family of proteins consists of delta-endotoxins expressed during sporulation of several subspecies of Bacillus thuringiensis. Its members possess insecticidal, hemolytic and cytolytic activities through pore formation, and attract attention due to their potential use as vehicles for targeted membrane-destruction. The delta-endotoxin of subsp. israelensis includes three Cyt species, a major Cyt1Aa and two minor proteins Cyt2Ba and Cyt1Ca. Cleaved Cyt protein that lacks the N- and C-terminal segments form toxic monomers. Here, we describe the crystal structure of Cyt2Ba, cleaved at its amino and carboxy terminus by bacterial endogenous protease(s). Overall, its fold resembles that of the previously described and the non-toxic form of . The structural similarity between these three proteins may provide information regarding the mechanism(s) of membrane perforating toxins. Cyt2Ba monomer (lavender) and Cyt2Aa dimer (monomer A - red and monomer B - blue) (PDB accession code 1cby) are shown. Note, the N-terminal intertwined strands and the C-terminal helices of Cyt2Aa are involved in dimer formation. Both segments do not exist in the proteolytically cleaved Cyt2Ba structure.