1.C.78 The Crystal Protein (Cry) Family

Crystal proteins of Bacillus thuringiensis form pores in lepidopteran larvae and have insecticidal activity (Brown and Whiteley, 1992; Okumura et al., 2006). They form discrete families, some of which are related to other cytotoxins from a variety of bacteria.

The generalized transport reaction is:

ions (in) ions (out)

This family belongs to the Aerolysin Superfamily.



Brown K.L. and H.R. Whiteley. (1992). Molecular Characterization of Two Novel Crystal Protein Genes from Bacillus thuringiensis subsp. thompsoni. J. Bacteriol. 174: 549-557.

Moar, W.J., A.J. Evans, C.R. Kessenich, J.A. Baum, D.J. Bowen, T.C. Edrington, J.A. Haas, J.K. Kouadio, J.K. Roberts, A. Silvanovich, Y. Yin, B.E. Weiner, K.C. Glenn, and M.L. Odegaard. (2016). The sequence, structural, and functional diversity within a protein family and implications for specificity and safety: The case for ETX_MTX2 insecticidal proteins. J Invertebr Pathol. [Epub: Ahead of Print]

Okumura S., H. Saitoh, N. Wasano, H. Katayama, K. Higuchi, E. Mizuki, K. Inouye. (2006). Efficient solubilization, activation, and purification of recombinant Cry45Aa of Bacillus thuringiensis expressed as inclusion bodies in Escherichia coli. Protein Expr. Purif. 47: 144-51.

Xu, C., U. Chinte, L. Chen, Q. Yao, Y. Meng, D. Zhou, L.J. Bi, J. Rose, M.J. Adang, B.C. Wang, Z. Yu, and M. Sun. (2015). Crystal structure of Cry51Aa1: A potential novel insecticidal aerolysin-type β-pore-forming toxin from Bacillus thuringiensis. Biochem. Biophys. Res. Commun. 462: 184-189.


TC#NameOrganismal TypeExample
1.C.78.1.1Pesticidal crystal protein (insecticidal δ-endotoxin), Cry15AaGram-positive bacteriaCry15Aa of Bacillus thuringiensis (Q45729)
1.C.78.1.2Crystal protein, CryET33BacteriaCryET33 of Bacillus thuringiensis (Q9KKG8)
1.C.78.1.3Parasporin 1470DBacteriaParasporin of Bacillus thuringiensis (Q6L5X8)

CRY51Aa insecticidal aerolysin-type β-pore-forming toxin of 309 aas.  The crystal structure is available (Xu et al. 2015).  Cry35 and Cry51 belong to protein families (Toxin_10, ETX_MTX2) sharing a common β-pore forming structure and function with known mammalian toxins such as epsilon toxin (ETX) (Moar et al. 2016).

Bacteria; firmicutes

Cry51Aa of Bacillus thuringiensis