Phylogenetic analysis and homology modelling of a new Cry8A crystal protein expressed in a sporulating soil bacterium

[Display omitted] •Protein profile of a spore producing soil isolate (BV5) was determined by SDS-PAGE.•Partial nucleotide sequence of amplified PCR fragment showed homology with Cry8 genes.•SDS-PAGE and MALDI-TOF mass spectrometry confirmed the expression of a matching protein.•Bioassay against coleopteran Anthonomus grandis (Cry8A target) showed no activity.•A series of mutations in one of the variable loops on the surface of the protein is suggested. Cry proteins, commonly found in Gram-positive soil bacteria, are used worldwide as aerial sprays or in transgenic plants for controlling crop pest populations and insect vectors. Via PCR analysis, a spore producing soil isolate (BV5) was speculated to encode a Cry gene. Partial nucleotide sequence of the amplified PCR fragment showed homology with the Cry8 genes present in GenBank. A full-length Cry gene was cloned, and the predicted protein sequence grouped the newly isolated Cry protein with other Cry8A present in GenBank with a high possibility of it being a new Cry8. SDS-PAGE and MALDI-TOF mass spectrometry confirmed the expression of a single 135 KDa protein matching uniquely to the putative protein sequence of the BV5 Cry gene. However, bioassay against the coleopteran Anthonomus grandis (Coleopterans are a known Cry8A target), showed no activity. Phylogenetic analysis and homology modelling was performed to characterize the protein structure and function. These analyses suggest a series of mutations in one of the variable loops on the surface of the protein.