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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

Suppression of MDH aggregation by citrate-coated gold nanoparticles combined with Hsp70.1 μM MDH was suspended in assay buffer in the absence or mixed with 1.3 μM Hsp70 or AuNPs (10 μgmL-1); and a combination of Hsp70 and AuNPs, respectively. The suspensions were subjected to heat stress at 48°C for 20 minutes. The soluble fraction (S) was separated from pellet fraction (P) by centrifugation. Samples were analysed by SDS-PAGE analysis.
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pone.0121243.g006: Suppression of MDH aggregation by citrate-coated gold nanoparticles combined with Hsp70.1 μM MDH was suspended in assay buffer in the absence or mixed with 1.3 μM Hsp70 or AuNPs (10 μgmL-1); and a combination of Hsp70 and AuNPs, respectively. The suspensions were subjected to heat stress at 48°C for 20 minutes. The soluble fraction (S) was separated from pellet fraction (P) by centrifugation. Samples were analysed by SDS-PAGE analysis.

Mentions: Hsp70 proteins act as molecular chaperones that suppress protein aggregation as well as refold misfolded proteins [35]. Previously, we observed that cysteine-coated AuNPs did not interfere with the chaperone function of human Hsp70 [19]. In the current study, we sought to investigate the effect of citrate-coated AuNPs on the function of another DnaK/Hsp70 homologue, Plasmodium falciparum Hsp70 [25][31] that is known to possess chaperone function [36]. As expected, the Hsp70 chaperone promoted the retention of MDH in soluble form (Fig. 6; lane “Hsp70”). In addition, the heat-induced aggregation of MDH was significantly suppressed by the citrate AuNPs (Fig. 6; lane “AuNPs”). A mixture of the Hsp70 chaperone and AuNPs also suppressed the aggregation of MDH (Fig. 6; lanes “AuNPs+Hsp70”). This suggests that the AuNPs at this concentration (10 μgmL-1) did not interfere with Hsp70 function. These findings suggest that the citrate-coated AuNPs are capable of suppressing MDH aggregation in vitro as we previously observed with cysteine-coated AuNPs [19].


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

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

Suppression of MDH aggregation by citrate-coated gold nanoparticles combined with Hsp70.1 μM MDH was suspended in assay buffer in the absence or mixed with 1.3 μM Hsp70 or AuNPs (10 μgmL-1); and a combination of Hsp70 and AuNPs, respectively. The suspensions were subjected to heat stress at 48°C for 20 minutes. The soluble fraction (S) was separated from pellet fraction (P) by centrifugation. Samples were analysed by SDS-PAGE analysis.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0121243.g006: Suppression of MDH aggregation by citrate-coated gold nanoparticles combined with Hsp70.1 μM MDH was suspended in assay buffer in the absence or mixed with 1.3 μM Hsp70 or AuNPs (10 μgmL-1); and a combination of Hsp70 and AuNPs, respectively. The suspensions were subjected to heat stress at 48°C for 20 minutes. The soluble fraction (S) was separated from pellet fraction (P) by centrifugation. Samples were analysed by SDS-PAGE analysis.
Mentions: Hsp70 proteins act as molecular chaperones that suppress protein aggregation as well as refold misfolded proteins [35]. Previously, we observed that cysteine-coated AuNPs did not interfere with the chaperone function of human Hsp70 [19]. In the current study, we sought to investigate the effect of citrate-coated AuNPs on the function of another DnaK/Hsp70 homologue, Plasmodium falciparum Hsp70 [25][31] that is known to possess chaperone function [36]. As expected, the Hsp70 chaperone promoted the retention of MDH in soluble form (Fig. 6; lane “Hsp70”). In addition, the heat-induced aggregation of MDH was significantly suppressed by the citrate AuNPs (Fig. 6; lane “AuNPs”). A mixture of the Hsp70 chaperone and AuNPs also suppressed the aggregation of MDH (Fig. 6; lanes “AuNPs+Hsp70”). This suggests that the AuNPs at this concentration (10 μgmL-1) did not interfere with Hsp70 function. These findings suggest that the citrate-coated AuNPs are capable of suppressing MDH aggregation in vitro as we previously observed with cysteine-coated AuNPs [19].

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