Dataset Information

Improvement of crystal solubility and increasing toxicity against Caenorhabditis elegans by asparagine substitution in block 3 of Bacillus thuringiensis crystal protein Cry5Ba.

ABSTRACT: The crystal proteins from Bacillus thuringiensis are widely used for their specific toxicity against insects and nematodes. The highly conserved sequence blocks play an important role in Cry protein stability and flexibility, the basis of toxicity. The block 3 in Cry5Ba subfamily has a shorter sequence (only 12 residues) and more asparagine residues than that of others which harbor about 48 residues but only one asparagine. Based on the theoretical structure model of Cry5Ba, all three asparagines in block 3 are closely located in the interface of putative three domains, implying their probable importance in structure and function. In this study, all three asparagines in Cry5Ba2 block 3 were individually substituted with alanine by site-directed mutagenesis. The wild-type and mutant proteins were overexpressed and crystallized in acrystalliferous B. thuringiensis strain BMB171. However, the crystals formed in one of the mutants, designated N586A, abnormally disappeared and dissolved into the culture supernatant once the sporulation cells lysed, whereas the Cry5Ba crystal and the other mutant crystals were stable. The mutant N586A crystal, isolated from sporulation cells by the ultrasonic process, was found to be easily dissolved at wide range of pH value (5.0 to 10.0). Moreover, the toxicity assays showed that the mutant N586A exhibited nearly 9-fold-higher activity against nematodes and damaged the host's intestine more efficiently than the native Cry5Ba2. These data support the presumption that the amide residue Asn586 at the interface of domains might adversely affect the protein flexibility, solubility and resultant toxicity of Cry5Ba.

SUBMITTER: Wang F

PROVIDER: S-EPMC3457124 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Improvement of crystal solubility and increasing toxicity against Caenorhabditis elegans by asparagine substitution in block 3 of Bacillus thuringiensis crystal protein Cry5Ba.

Wang Fenshan F Liu Yingying Y Zhang Fengjuan F Chai Lujun L Ruan Lifang L Peng Donghai D Sun Ming M

Applied and environmental microbiology 20120803 20

The crystal proteins from Bacillus thuringiensis are widely used for their specific toxicity against insects and nematodes. The highly conserved sequence blocks play an important role in Cry protein stability and flexibility, the basis of toxicity. The block 3 in Cry5Ba subfamily has a shorter sequence (only 12 residues) and more asparagine residues than that of others which harbor about 48 residues but only one asparagine. Based on the theoretical structure model of Cry5Ba, all three asparagine ...[more]

PMID: 22865071

Similar Datasets

Project description:In the past decade, the paradigm which claimed that invertebrate immune systems lack specificity has been reconsidered. Accumulating evidence supports that invertebrate immune systems are able to mount specific responses to the pathogen species-, and even to the pathogen strain-level. However, the underlying molecular mechanisms behind invertebrate immune specificity remain mostly unknown. Studying the molecular basis of invertebrate immune specificity in a genetically tractable model, such as the nematode Caenorhabditis elegans, has the potential to reveal insights into the immune systems of other metazoans, including humans. We chose to study the mechanisms of specific immune responses of the worm to two different pathogenic strains of the Gram-positive bacterium Bacillus thuringiensis (MYBY18247 and MYBT18679), because there is phenotypic evidence of specific genotype-genotype interactions between this host-pathogen pair. We did an initial RNA-Seq experiment upon pathogen exposure and found that 9% of the differentially expressed genes change their expression in different ways when comparing the two pathogen strains. Through promoter region motif enrichment analysis, we found the GATA transcription factor ELT-2 is responsible for the pathogen strain-specific transcriptomic response. Upon elt-2 knockdown worms exposed to MYBT18679 display lower survival rate coupled with higher intestinal damage than non-infected controls. Additionally, by performing further genetic analysis using gene knockdown and knockout, we found that the p38 MAPK pathway acts likely in parallel to elt-2 and the transcription factor skn-1 cooperates with elt-2 to promote resistance to MYBT18679. On the other hand, elt-2 knockdown leads to a substantially higher survival rate, together with lower intestinal tissue damage compared to control worms, upon exposure to MYBT18247, another pathogenic Bacillus thuringiensis strain. The MYBT18247 pathogen load of elt-2(RNAi) worms compared to control worms remained unchanged, suggesting the elt-2 negatively regulates tolerance towards MYBT18247. We found that tolerance to MYBT18247 was positively regulated by the transcription factors: FOXO daf-16, bZip zip-2, nhr-99 and nhr-193. To identify elt-2 negatively-regulated downstream targets that could promote tolerance to MYBT18247, we performed a second RNA-Seq experiment, this time including elt-2(RNAi) worms exposed to both pathogenic strains. We found four genes negatively regulated by elt-2: cdr-2, poml-3, dhs-30 and tre-3, with putative function in detoxification and lipid metabolism, which can mediate tolerance to MYBT18247. We conclude that ELT-2 coordinates strain-specific immune responses in this invertebrate host and promotes resistance upon exposure to MYBT18679, while it negatively regulates tolerance to MYBT18247. The response is likely to be specific to the crystal pore-forming toxins produced by this pathogen.

Dataset Information

Improvement of crystal solubility and increasing toxicity against Caenorhabditis elegans by asparagine substitution in block 3 of Bacillus thuringiensis crystal protein Cry5Ba.

Publications

Improvement of crystal solubility and increasing toxicity against Caenorhabditis elegans by asparagine substitution in block 3 of Bacillus thuringiensis crystal protein Cry5Ba.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets