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DnaK protein alleviates toxicity induced by citrate-coated gold nanoparticles in Escherichia coli.

Makumire S, Revaprasadu N, Shonhai A - PLoS ONE (2015)

Bottom Line: We further investigated the effects of the AuNPs on the solubility of the E. coli BB1553 proteome.The toxic effects of the AuNPs were alleviated by transforming the E. coli BB1553 cells with a construct expressing DnaK.Our study suggests a role for DnaK in alleviating nanoparticle induced stress in E. coli.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, School of Mathematics & Natural Sciences, University of Venda, Thohoyandou, South Africa; Department of Biochemistry & Microbiology, University of Zululand, KwaDlangezwa, South Africa.

ABSTRACT
A number of previously reported studies suggest that synthetic gold nanoparticles (AuNPs) are capable of stabilising proteins against heat stress in vitro. However, it remains to be understood if AuNPs confer stability to proteins against cellular stress in vivo. Heat shock proteins (Hsps) are conserved molecules whose main role is to facilitate folding of other proteins (chaperone function). Hsp70 (called DnaK in prokaryotes) is one of the most prominent molecular chaperones. Since gold nanoparticles exhibit chaperone-like function in vitro, we investigated the effect of citrate-coated gold nanoparticles on the growth of E. coli BB1553 cells that possess a deleted dnaK gene. We further investigated the effects of the AuNPs on the solubility of the E. coli BB1553 proteome. E. coli BB1553 cells exposed to AuNPs exhibited cellular defects such as filamentation and plasma membranes pulled off the cell wall. The toxic effects of the AuNPs were alleviated by transforming the E. coli BB1553 cells with a construct expressing DnaK. We also noted that cells in which DnaK was restored exhibited distinct zones to which the nanoparticles were restricted. Our study suggests a role for DnaK in alleviating nanoparticle induced stress in E. coli.

No MeSH data available.


Related in: MedlinePlus

TEM and HRTEM images of synthesised citrate-coated gold nanoparticle 0.3 mM gold salt was reduced with 136 mM tri-sodium citrate.(A) Absorption spectra of citrate capped AuNPs; the insert shows the red wine suspensions obtained. (B) TEM images of the citrate AuNPs (top panel), and HRTEM images of AuNPs (lower panel). The presence of visibly defined lattice fringes confirmed the crystal morphology of the nanoparticles produced. (C) Bar graph representing the frequency of the citrate capped AuNPs by size.
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pone.0121243.g001: TEM and HRTEM images of synthesised citrate-coated gold nanoparticle 0.3 mM gold salt was reduced with 136 mM tri-sodium citrate.(A) Absorption spectra of citrate capped AuNPs; the insert shows the red wine suspensions obtained. (B) TEM images of the citrate AuNPs (top panel), and HRTEM images of AuNPs (lower panel). The presence of visibly defined lattice fringes confirmed the crystal morphology of the nanoparticles produced. (C) Bar graph representing the frequency of the citrate capped AuNPs by size.

Mentions: The absorption spectrum of the citrate-coated AuNPs synthesised is shown on Fig. 1A. The absorption peak at 519 nm (Fig. 1A), is assigned to the surface plasmon absorption spectrum of AuNPs which ranges between 510–530 nm [32]. The spectrum appeared narrow suggesting a narrow range of the diameters of the particles obtained. High citrate concentrations are known to limit the growth of nanoparticles [33]. It is possible that the citrate concentration used in this study (136 mM) could have resulted in smaller nanoparticles with a narrow size range. As observed under TEM, the synthesised citrate AuNPs were consistently spherical and mono-dispersed (Fig. 1B, top panel). The representation of the nanoparticles obtained based on their sizes is shown (Fig. 1C). The nanoparticles exhibited an average diameter of 16.2 nm with a standard deviation of ± 2.59 nm. The HRTEM image showed distinctly defined lattice fringes confirming the crystalline nature of the particles (Fig. 1B, lower panel). At higher resolution, the presence of a layer around the particles was also evidently visible suggesting the presence of a citrate coating on the nanoparticle surface.


DnaK protein alleviates toxicity induced by citrate-coated gold nanoparticles in Escherichia coli.

Makumire S, Revaprasadu N, Shonhai A - PLoS ONE (2015)

TEM and HRTEM images of synthesised citrate-coated gold nanoparticle 0.3 mM gold salt was reduced with 136 mM tri-sodium citrate.(A) Absorption spectra of citrate capped AuNPs; the insert shows the red wine suspensions obtained. (B) TEM images of the citrate AuNPs (top panel), and HRTEM images of AuNPs (lower panel). The presence of visibly defined lattice fringes confirmed the crystal morphology of the nanoparticles produced. (C) Bar graph representing the frequency of the citrate capped AuNPs by size.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383610&req=5

pone.0121243.g001: TEM and HRTEM images of synthesised citrate-coated gold nanoparticle 0.3 mM gold salt was reduced with 136 mM tri-sodium citrate.(A) Absorption spectra of citrate capped AuNPs; the insert shows the red wine suspensions obtained. (B) TEM images of the citrate AuNPs (top panel), and HRTEM images of AuNPs (lower panel). The presence of visibly defined lattice fringes confirmed the crystal morphology of the nanoparticles produced. (C) Bar graph representing the frequency of the citrate capped AuNPs by size.
Mentions: The absorption spectrum of the citrate-coated AuNPs synthesised is shown on Fig. 1A. The absorption peak at 519 nm (Fig. 1A), is assigned to the surface plasmon absorption spectrum of AuNPs which ranges between 510–530 nm [32]. The spectrum appeared narrow suggesting a narrow range of the diameters of the particles obtained. High citrate concentrations are known to limit the growth of nanoparticles [33]. It is possible that the citrate concentration used in this study (136 mM) could have resulted in smaller nanoparticles with a narrow size range. As observed under TEM, the synthesised citrate AuNPs were consistently spherical and mono-dispersed (Fig. 1B, top panel). The representation of the nanoparticles obtained based on their sizes is shown (Fig. 1C). The nanoparticles exhibited an average diameter of 16.2 nm with a standard deviation of ± 2.59 nm. The HRTEM image showed distinctly defined lattice fringes confirming the crystalline nature of the particles (Fig. 1B, lower panel). At higher resolution, the presence of a layer around the particles was also evidently visible suggesting the presence of a citrate coating on the nanoparticle surface.

Bottom Line: We further investigated the effects of the AuNPs on the solubility of the E. coli BB1553 proteome.The toxic effects of the AuNPs were alleviated by transforming the E. coli BB1553 cells with a construct expressing DnaK.Our study suggests a role for DnaK in alleviating nanoparticle induced stress in E. coli.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, School of Mathematics & Natural Sciences, University of Venda, Thohoyandou, South Africa; Department of Biochemistry & Microbiology, University of Zululand, KwaDlangezwa, South Africa.

ABSTRACT
A number of previously reported studies suggest that synthetic gold nanoparticles (AuNPs) are capable of stabilising proteins against heat stress in vitro. However, it remains to be understood if AuNPs confer stability to proteins against cellular stress in vivo. Heat shock proteins (Hsps) are conserved molecules whose main role is to facilitate folding of other proteins (chaperone function). Hsp70 (called DnaK in prokaryotes) is one of the most prominent molecular chaperones. Since gold nanoparticles exhibit chaperone-like function in vitro, we investigated the effect of citrate-coated gold nanoparticles on the growth of E. coli BB1553 cells that possess a deleted dnaK gene. We further investigated the effects of the AuNPs on the solubility of the E. coli BB1553 proteome. E. coli BB1553 cells exposed to AuNPs exhibited cellular defects such as filamentation and plasma membranes pulled off the cell wall. The toxic effects of the AuNPs were alleviated by transforming the E. coli BB1553 cells with a construct expressing DnaK. We also noted that cells in which DnaK was restored exhibited distinct zones to which the nanoparticles were restricted. Our study suggests a role for DnaK in alleviating nanoparticle induced stress in E. coli.

No MeSH data available.


Related in: MedlinePlus