A new insight into mercurized hemoglobin aggregation mechanism

Myshkin, A. E.; Khromova, Vera S.

doi:10.1016/j.bbapap.2005.01.008

Cited by 4 publications

(6 citation statements)

References 6 publications

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“…In particular, a protein band likely corresponding to a Hb tetramer on the basis of its apparent MW was observable. These data are in agreement with the reported Hg-induced protein coagulation effect on purified bovine Hb, incubated in vitro in the presence of mercuric acetate [ 46 ]. At this stage of investigation, we do not provide direct evidence of increased or decreased oxygen affinity for mercurized-Hb.…”

Section: Discussionsupporting

confidence: 93%

Novel Insights into Mercury Effects on Hemoglobin and Membrane Proteins in Human Erythrocytes

et al. 2020

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Mercury (Hg) is a global environmental pollutant that affects human and ecosystem health. With the aim of exploring the Hg-induced protein modifications, intact human erythrocytes were exposed to HgCl2 (1–60 µM) and cytosolic and membrane proteins were analyzed by SDS-PAGE and AU-PAGE. A spectrofluorimetric assay for quantification of Reactive Oxygen Species (ROS) generation was also performed. Hg2+ exposure induces alterations in the electrophoretic profile of cytosolic proteins with a significant decrease in the intensity of the hemoglobin monomer, associated with the appearance of a 64 kDa band, identified as a mercurized tetrameric form. This protein decreases with increasing HgCl2 concentrations and Hg-induced ROS formation. Moreover, it appears resistant to urea denaturation and it is only partially dissociated by exposure to dithiothreitol, likely due to additional protein–Hg interactions involved in aggregate formation. In addition, specific membrane proteins, including band 3 and cytoskeletal proteins 4.1 and 4.2, are affected by Hg2+-treatment. The findings reported provide new insights into the Hg-induced possible detrimental effects on erythrocyte physiology, mainly related to alterations in the oxygen binding capacity of hemoglobin as well as decreases in band 3-mediated anion exchange. Finally, modifications of cytoskeletal proteins 4.1 and 4.2 could contribute to the previously reported alteration in cell morphology.

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Section: Discussionsupporting

confidence: 93%

Novel Insights into Mercury Effects on Hemoglobin and Membrane Proteins in Human Erythrocytes

et al. 2020

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“…On the other hand, Myshkin and Khromova found that the rate of Hg 2+ ‐induced aggregation of hemoglobin declined with increasing pH over the 7.2–8.1 range . They interpreted this as OH − binding to Hg 2+ and hindering its ability to bind to the protein.…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, Myshkin and Khromova found that the rate of Hg 21 -induced aggregation of hemoglobin declined with increasing pH over the 7.2-8.1 range. 23 They interpreted this as OH 2 binding to Hg 21 and hindering its ability to bind to the protein. However, these same authors showed that Tris buffer binds to Hg 21 , displacing one of its protein ligands and inhibiting aggregation.…”

Section: Discussionmentioning

confidence: 99%

“…Myshkin et al have found that the metal‐induced aggregation of hemoglobin depends on Hg 2+ binding to a noncysteine side chain along with cysteine‐β93, and that interfering with Hg 2+ ‐non‐cysteine binding protects against aggregation . Because Hg 2+ binding to cysteine thiols is already well‐characterized, we set out to study Hg 2+ inhibition of enzymes that lack accessible cysteine sites.…”

Section: Introductionmentioning

confidence: 99%

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Mercury(II) binds to both of chymotrypsin's histidines, causing inhibition followed by irreversible denaturation/aggregation

et al. 2017

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The toxicity of mercury is often attributed to its tight binding to cysteine thiolate anions in vital enzymes. To test our hypothesis that Hg(II) binding to histidine could be a significant factor in mercury's toxic effects, we studied the enzyme chymotrypsin, which lacks free cysteine thiols; we found that chymotrypsin is not only inhibited, but also denatured by Hg(II). We followed the aggregation of denatured enzyme by the increase in visible absorbance due to light scattering. Hg(II)-induced chymotrypsin precipitation increased dramatically above pH 6.5, and free imidazole inhibited this precipitation, implicating histidine-Hg(II) binding in the process of chymotrypsin denaturation/aggregation. Diethylpyrocarbonate (DEPC) blocked chymotrypsin's two histidines (his and his ) quickly and completely, with an IC of 35 ± 6 µM. DEPC at 350 µM reduced the hydrolytic activity of chymotrypsin by 90%, suggesting that low concentrations of DEPC react with his at the active site catalytic triad; furthermore, DEPC below 400 µM enhanced the Hg(II)-induced precipitation of chymotrypsin. We conclude that his reacts readily with DEPC, causing enzyme inhibition and enhancement of Hg(II)-induced aggregation. Above 500 µM, DEPC inhibited Hg(II)-induced precipitation, and [DEPC] >2.5 mM completely protected chymotrypsin against precipitation. This suggests that his reacts less readily with DEPC, and that chymotrypsin denaturation is caused by Hg(II) binding specifically to the his residue. Finally, we show that Hg(II)-histidine binding may trigger hemoglobin aggregation as well. Because of results with these two enzymes, we suggest that metal-histidine binding may be key to understanding all heavy metal-induced protein aggregation.

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“…It was reported that peroxidases are inhibited by heavy metal ions at higher concentrations [25] and Hg 2+ ion is listed as the most effective inhibitor [26] [27]. Konyaeva et al reported that Hg 2+ chelators like EDTA can protect hemoglobin against Hg 2+ -induced denaturation and precipitation [28].…”

Section: Introductionmentioning

confidence: 99%

New Ionic Liquids with Buffering and Chelating Abilities for Enzyme Engineering

Ou¹,

He²

2019

ABB

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Ionic liquids (ILs) with buffering and chelating abilities were designed and synthesized on the basis of ethylenediaminetetraacetic acid (EDTA) for the development of buffered enzymatic IL systems and for enzymatic reaction in heavy metal containing aqueous system. Transesterification activity of Candida antarctica lipase B dissolved in the hydroxyl-functionalized IL was buffer dependent. High activity and outstanding stability was obtained with the buffered enzymatic IL systems for the transesterification. In heavy metal containing aqueous system, EDTA IL buffers as Hg 2+ chelators protected horseradish peroxidase (HRP) against Hg 2+-induced denaturation and precipitation. Higher pH favored the protection, while at lower pH the protection diminished. We can conclude that the new ILs possess both buffering and chelating abilities.

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A new insight into mercurized hemoglobin aggregation mechanism

Cited by 4 publications

References 6 publications

Novel Insights into Mercury Effects on Hemoglobin and Membrane Proteins in Human Erythrocytes

Novel Insights into Mercury Effects on Hemoglobin and Membrane Proteins in Human Erythrocytes

Mercury(II) binds to both of chymotrypsin's histidines, causing inhibition followed by irreversible denaturation/aggregation

New Ionic Liquids with Buffering and Chelating Abilities for Enzyme Engineering

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