Homology modeling of mosquitocidal Cry30Ca2 of Bacillus thuringiensis and its molecular docking with N-acetylgalactosamine

Abstract

Objective: To investigate the theoretical model of the three-dimensional structure of mosquitocidal Cry30Ca2 and its molecular docking with N-acetylgalactosamine.

Methods: The theoretical model of Cry30Ca2 was predicted by homology modeling on the structure of the Cry4Ba. Docking studies were performed to investigate the interaction of Cry30Ca2 with N-acetylgalactosamine on the putative receptor.

Results: Cry30Ca2 toxin is a rather compact molecule composed of three distinct domains and has approximate overall dimensions of 95 by 75 by 60Å. Domain II is a helix bundle, Domain II consists of three antiparallel β-sheets, Domain III is composed of two β-sheets that adopt a β-sandwich fold. Residue 321Ile in loop1, residues 342Gln 343Thr and 345Gln in loop2, residue 393Tyr in loop3 of Cry30Ca2 are responsible for the interactions with GalNAc via 7 hydrogen bonds, 6 of them were related to the oxygen atoms of hydroxyls of the ligand, and one to the nitrogen of the ligand.

Conclusion: The 3D structure of Cry30Ca2 resembles the previously reported Cry toxin structures but shows still some distinctions. Several residues in the loops of the apex of domain II are responsible for the interactions with N-acetylgalactosamine.