The Insecticidal Proteins of Bacillus thuringiensis

A review of the environmental safety of the Cry1Ac protein

“…The crystal structure of Cry1Aa has been determined and shows a high degree of structural similarity to other known Cry protein structures (Cry3A, Cry2A, Cry4A, and Cry4B) despite sequence identities that can fall below 30% (Aronson and Shai, 2001;Bravo et al, 2007;Crickmore et al, 1998;Kumar et al, 1996;OECD, 2007). In the original nomenclature, the Cry proteins were designated based on their insecticidal activity (CryI proteins were those active against lepidopterans), and although the nomenclature is now sequence dependent the target specificity remains largely intact such that proteins designated Cry1 have activity specifically against lepidopterans (Aronson and Shai, 2001;Crickmore et al, 1998;Hofte and Whiteley, 1989;Kumar et al, 1996;OECD, 2007).…”

“…Preparations of natural isolates of B. thuringiensis were first used as a commercial insecticide in France in 1938 and B. thuringiensis subspecies kurstaki (which produces Cry1Ac among other Cry proteins) has been registered with US EPA since 1961 (Kumar et al, 1996;Schnepf et al, 1998;USEPA, 2001). Microbial preparations of 4 also called thuringiensin B. thuringiensis are currently approved for use around the world including in Australia, Canada, the European Union, and the United States (AVPMA, 2010;EU DG SANCO, 2010;PMRA, 2008;USEPA, 2001).…”

“…The Cry protein δ endotoxins are so named because they are the primary component of the protein parasporal crystals that are characteristic of spore formation in B. thuringiensis (Hofte and Whiteley, 1989;Kumar et al, 1996;Schnepf et al, 1998;OECD, 2007). A systematic nomenclature for identifying and differentiating Cry MON-15985-7 MON 15985 X X X X X X DAS-21023-5 3006-210-23 X 31807/31808 X X DAS-21023-5 x DAS-24236-5 X X DAS-21023-5 x DAS-24236-5 x MON-01445-2 proteins was proposed in 1989 and widely adopted (Hofte and Whiteley, 1989;OECD, 2007).…”

“…Although there is significant variability in amino acid sequence and target range, the general mechanism by which Cry proteins (including Cry1Ac) achieve insecticidal activity is believed to be common across the group (Aronson and Shai, 2001;Bravo et al, 2007;Crickmore et al, 1998Crickmore et al, , 2005Hofte and Whiteley, 1989;Kumar et al, 1996;OECD, 2007). The Cry1 proteins are produced in the form of protoxins of 130-140 kDa in size containing 1100-1200 amino acid residues (Aronson and Shai, 2001;Bravo et al, 2007;Kumar et al, 1996;OECD, 2007).…”

“…The Cry1 proteins are produced in the form of protoxins of 130-140 kDa in size containing 1100-1200 amino acid residues (Aronson and Shai, 2001;Bravo et al, 2007;Kumar et al, 1996;OECD, 2007). For Cry1A these protoxins are cleaved to generate active toxins consisting of 60-70 kDa fragments from the N terminal portion of the protein (Knowles, 1994;Kumar et al, 1996).…”