Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Differential thermal stability and oxidative vulnerability of the hemoglobin variants, HbA2 and HbE.

ABSTRACT: Apart from few early biophysical studies, the relative thermal instability of HbE has been only shown by clinical investigations. We have compared in vitro thermal stability of HbE with HbA2 and HbA using optical spectroscopy. From absorption measurements in the soret region, synchronous fluorescence spectroscopy and dynamic light scattering experiments, we have found thermal stability of the three hemoglobin variants following the order HbE11.0 in all the three variants. Under oxidative stress conditions in presence of hydrogen peroxide, HbE has been found to be more vulnerable to aggregation compared to HbA and HbA2. Taken together, these studies have shown thermal and oxidative instability of HbE and points towards the role of HbE in the upregulation of redox regulators and chaperone proteins in erythrocyte proteome of patients suffering from HbEbeta thalassemia.

SUBMITTER: Chakrabarti A

PROVIDER: S-EPMC3828284 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Differential thermal stability and oxidative vulnerability of the hemoglobin variants, HbA2 and HbE.

Chakrabarti Abhijit A Bhattacharya Dipankar D Deb Sanghamitra S Chakraborty Madhumita M

PloS one 20131114 11

Apart from few early biophysical studies, the relative thermal instability of HbE has been only shown by clinical investigations. We have compared in vitro thermal stability of HbE with HbA2 and HbA using optical spectroscopy. From absorption measurements in the soret region, synchronous fluorescence spectroscopy and dynamic light scattering experiments, we have found thermal stability of the three hemoglobin variants following the order HbE<HbA<HbA2 in terms of structural unfolding and aggregat ...[more]

PMID: 24244748

Similar Datasets

De novo alpha 2 hemoglobin gene (HBA2) mutation in a child with hemoglobin M Iwate and symptomatic methemoglobinemia since birth.

Project description:Cyanosis in an apparently healthy newborn baby may be caused by hemoglobin variants associated with the formation of methemoglobin, collectively known as M hemoglobins. They should not be confused with genetic alterations in methemoglobin reductase enzyme systems of red cells since treatment and prognosis are completely different. A newborn male child was noted to be significantly cyanotic at birth and is the basis for this report. Hemoglobin isoelectric focusing, acid and alkaline gel electrophoresis, and HBA/HBB gene sequencing were performed for the child, both parents and a sister. The newborn child was treated with methylene blue in an intensive care unit fearing that he had a defective reductase system and exposure to oxidant drugs or toxins. Newborn hemoglobin screening with high performance liquid chromatography was abnormal on the 10th and 45th days but no conclusive diagnosis was reached. Cyanosis persisted up to four years of age with no other symptoms. Hemoglobin M Iwate [alpha2 87(F8) His>Tyr, HBA2:c.262C>T] was detected. It was not present in the child's presumed mother, father, sister, and brother. The analysis of 15 short tandem repeats in the trio demonstrated a de novo mutation occurrence (p-value<1×10(-8)). The family was reassured that no further action was necessary and genetic counseling was provided. Methemoglobins should be considered for differential diagnosis of cyanosis in newborns even if no familial cases are detected. Except for cosmetic consequences, the clinical course of patients with hemoglobin M Iwate is unremarkable.

| S-EPMC4109735 | biostudies-literature

Oxidative instability of hemoglobin E (β26 Glu→Lys) is increased in the presence of free α subunits and reversed by α-hemoglobin stabilizing protein (AHSP): Relevance to HbE/β-thalassemia.

Project description:When adding peroxide (H2O2), β subunits of hemoglobin (Hb) bear the burden of oxidative changes due in part to the direct oxidation of its Cys93. The presence of unpaired α subunits within red cells and/or co-inheritance of another β subunit mutant, HbE (β26 Glu→Lys) have been implicated in the pathogenesis and severity of β thalassemia. We have found that although both HbA and HbE autoxidize at initially comparable rates, HbE loses heme at a rate almost 2 fold higher than HbA due to unfolding of the protein. Using mass spectrometry and the spin trap, DMPO, we were able to quantify irreversible oxidization of βCys93 to reflect oxidative instability of β subunits. In the presence of free α subunits and H2O2, both HbA and HbE showed βCys93 oxidation which increased with higher H2O2 concentrations. In the presence of Alpha-hemoglobin stabilizing protein (AHSP), which stabilizes the α-subunit in a redox inactive hexacoordinate conformation (thus unable to undergo the redox ferric/ferryl transition), Cys93 oxidation was substantially reduced in both proteins. These experiments establish two important features that may have relevance to the mechanistic understanding of these two inherited hemoglobinopathies, i.e. HbE/β thalassemia: First, a persistent ferryl/ferryl radical in HbE is more damaging to its own β subunit (i.e., βCys93) than HbA. Secondly, in the presence of excess free α-subunit and under the same oxidative conditions, these events are substantially increased for HbE compared to HbA, and may therefore create an oxidative milieu affecting the already unstable HbE.

| S-EPMC4804395 | biostudies-literature

Site-directed mutagenesis of cysteine residues alters oxidative stability of fetal hemoglobin.

Project description:Redox active cysteine residues including ?Cys93 are part of hemoglobin's "oxidation hotspot". Irreversible oxidation of ?Cys93 ultimately leads to the collapse of the hemoglobin structure and release of heme. Human fetal hemoglobin (HbF), similarly to the adult hemoglobin (HbA), carries redox active ?Cys93 in the vicinity of the heme pocket. Site-directed mutagenesis has been used in this study to examine the impact of removal and/or addition of cysteine residues in HbF. The redox activities of the recombinant mutants were examined by determining the spontaneous autoxidation rate, the hydrogen peroxide induced ferric to ferryl oxidation rate, and irreversible oxidation of cysteine by quantitative mass spectrometry. We found that substitution of ?Cys93Ala resulted in oxidative instability characterized by increased oxidation rates. Moreover, the addition of a cysteine residue at ?19 on the exposed surface of the ?-chain altered the regular electron transfer pathway within the protein by forming an alternative oxidative site. This may also create an accessible site for di-sulfide bonding between Hb subunits. Engineering of cysteine residues at suitable locations may be useful as a tool for managing oxidation in a protein, and for Hb, a way to stave off oxidation reactions resulting in a protein structural collapse.

| S-EPMC6126208 | biostudies-literature

Induction of fetal hemoglobin: Lentiviral shRNA knockdown of HBS1L in β0-thalassemia/HbE erythroid cells

Project description:Imbalanced globin chain output contributes to thalassemia pathophysiology. Hence, induction of fetal hemoglobin in β-thalassemia and other β-hemoglobinopathies are of continuing interest for therapeutic approaches. Genome-wide association studies have identified three common genetic loci: namely β-globin (HBB), an intergenic region between MYB and HBS1L, and BCL11A underlying quantitative fetal hemoglobin production. Here, we report that knockdown of HBS1L (all known variants) using shRNA in early erythroblast obtained from β0-thalassemia/HbE patients triggers an upregulation of γ-globin mRNA 1.69 folds. There is modest perturbation of red cell differentiation assessed by flow cytometry and morphology studies. The levels of α- and β-globin mRNAs are relatively unaltered. Knockdown of HBS1L also increases the percentage of fetal hemoglobin around 16.7 folds when compared to non-targeting shRNA. Targeting HBS1L is attractive because of the potent induction of fetal hemoglobin and the modest effect on cell differentiation.

| S-EPMC9994754 | biostudies-literature

Assessment of Thermal Stability of Mutant p53 Proteins via Differential Scanning Fluorimetry.

Project description:The p53 protein is a transcription factor that preserves the integrity of the genome. The TP53 gene has inactivating mutations in about 50% of all human cancers. Some missense mutations lead to decreased thermal stability in the p53 protein, its unfolding and aggregation under physiological conditions. A general understanding of the impact of point mutations on the stability and conformation of mutant p53 is essential for the design and development of small molecules that target specific p53 mutations. In this work, we determined the thermostability properties of some of the most common mutant forms of the p53 protein-p53(R273H), p53(R248Q), p53(R248W) and p53(Y220C)-that are often considered as attractive therapeutic targets. The results showed that these missense mutations lead to destabilization of the p53 protein and a decrease in its melting temperature.

| S-EPMC9862671 | biostudies-literature

Deferoxamine deconditioning increases neuronal vulnerability to hemoglobin.

Project description:Concomitant treatment with deferoxamine (DFO) protects neural cells from iron and heme-mediated oxidative injury, but also disrupts cell responses to iron loading that may be protective. We hypothesized that DFO treatment and withdrawal would subsequently increase neuronal vulnerability to hemoglobin. Pretreatment with DFO followed by its washout increased neuronal loss after subsequent hemoglobin exposure by 3-4-fold compared with control vehicle-pretreated cultures. This was associated with reduced ferritin induction by hemoglobin; expression of heme oxygenase-1, which catalyzes iron release from heme, was not altered. Increased neuronal loss was prevented by exogenous apoferritin or by continuing DFO or antioxidants throughout the experimental course. Cell nonheme iron levels after hemoglobin treatment were similar in DFO-pretreated and control cultures. These results indicate that DFO deconditions neurons and subsequently increases their vulnerability to heme-mediated injury. Its net effect after CNS hemorrhage may be highly dependent on the timing and duration of its administration. Withdrawal of DFO while heme or iron levels remain elevated may be deleterious, and may negate any benefit of prior concomitant therapy.

| S-EPMC7301423 | biostudies-literature

Differential thermal stability, conformational stability and unfolding behavior of Eis proteins from Mycobacterium smegmatis and Mycobacterium tuberculosis.

Project description:Eis (Enhanced Intracellular Survival) is an important aminoglycoside N-acetyltransferase enzyme contributing to kanamycin resistance in Mtb clinical isolates. Eis proteins from M. tuberculosis (RvEis) and M. smegmatis (MsEis) have 58% identical and 69% similar amino acid sequences and acetylate aminoglycosides at multiple amines. Both the Eis proteins are hexameric and composed of two symmetric trimers. RvEis has remarkable structural stability and heat-stable aminoglycoside acetyltransferase activity. Although the structure and biochemical properties of MsEis have been studied earlier, the detailed characterization of its acetyltransferase activity and structural stability is lacking. In this study, we have performed comparative analysis of structural stability and aminoglycoside acetyltransferase activity of RvEis and MsEis proteins. Unlike RvEis, MsEis undergoes a three-state unfolding induced by heat or chemical denaturants and involves self-association of partially unfolded oligomers to form high molecular weight soluble aggregates. MsEis is highly susceptible to chemical denaturants and unfolds completely at lower concentrations of GdmCl and urea when compared to RvEis. In contrast to RvEis, the oligomeric forms of MsEis are SDS sensitive. However, SDS treatment resulted in increased helix formation in MsEis than RvEis. MsEis shows lesser thermostable activity with a decreased efficiency of kanamycin acetylation in comparison to RvEis. Furthermore, overexpression of MsEis does not provide thermal resistance to M. smegmatis unlike RvEis. Collectively, this study reveals that homologous proteins from pathogenic and nonpathogenic mycobacteria follow different modes of unfolding and demonstrate differential structural stability and activity despite highly similar sequences and oligomeric organization.

| S-EPMC6433294 | biostudies-literature

Oxidative stability, thermal stability and acceptability of coconut oil flavored with essential oils from black pepper and ginger.

Project description:The present study investigates the oxidative and thermal stability of flavoured oils developed by incorporating essential oils from black pepper and ginger to coconut oil (CNO) at concentrations of 0.1 and 1.0% (CNOP-0.1, CNOP-1, CNOG-0.1, CNOG-1). The stability of oils were assessed in terms of free fatty acids, peroxide, p-anisidine, conjugated diene and triene values and compared with CNO without any additives and a positive control with synthetic antioxidant TBHQ (CNOT). It was found that the stability of CNOP-1 and CNOG-1 were comparable with CNOT at both study conditions. The possibility of flavoured oil as a table top salad oil was explored by incorporating the same in vegetable salad and was found more acceptable than the control, on sensory evaluation. The synergetic effect of essential oil as a flavour enhancer and a powerful natural antioxidant that can slow down the oxidation of fats was established in the study.

| S-EPMC5305711 | biostudies-literature

Down-regulation of the transcriptional repressor ZNF802 (JAZF1) reactivates fetal hemoglobin in β<sup>0</sup>-thalassemia/HbE.

Project description:Reactivating of fetal hemoglobin (HbF; α2γ2) can ameliorate the severity of β-thalassemia disease by compensating for adult hemoglobin deficiency in patients. Previously, microarray analysis revealed that zinc finger protein (ZNF)802 (also known as Juxta-posed with another zinc finger gene-1 (JAZF1)) was upregulated in human erythroblasts derived from adult peripheral blood compared with fetal liver-derived cells, implying a potential role as a HbF repressor. However, deficiency in ZNF802 induced by lentiviral shRNA in β0-thalassemia/hemoglobinE erythroblasts had no effect on erythroblast proliferation and differentiation. Remarkably, the induction of HBG expression was observed at the transcriptional and translational levels resulting in an increase of HbF to 35.0 ± 3.5%. Interestingly, the embryonic globin transcripts were also upregulated but the translation of embryonic globin was not detected. These results suggest ZNF802 might be a transcriptional repressor of the γ-globin gene in adult erythroid cells.

| S-EPMC8943019 | biostudies-literature

"Stable-on-the-Table" Biosensors: Hemoglobin-Poly (Acrylic Acid) Nanogel BioElectrodes with High Thermal Stability and Enhanced Electroactivity.

Project description:In our efforts toward producing environmentally responsible but highly stable bioelectrodes with high electroactivities, we report here a simple, inexpensive, autoclavable high sensitivity biosensor based on enzyme-polymer nanogels. Met-hemoglobin (Hb) is stabilized by wrapping it in high molecular weight poly(acrylic acid) (PAA, M(W) 450k), and the resulting nanogels abbreviated as Hb-PAA-450k, withstood exposure to high temperatures for extended periods under steam sterilization conditions (122 °C, 10 min, 17-20 psi) without loss of Hb structure or its peroxidase-like activities. The bioelectrodes prepared by coating Hb-PAA-450k nanogels on glassy carbon showed well-defined quasi-reversible redox peaks at -0.279 and -0.334 V in cyclic voltammetry (CV) and retained >95% electroactivity after storing for 14 days at room temperature. Similarly, the bioelectrode showed ~90% retention in electrochemical properties after autoclaving under steam sterilization conditions. The ultra stable bioelectrode was used to detect hydrogen peroxide and demonstrated an excellent detection limit of 0.5 μM, the best among the Hb-based electrochemical biosensors. This is the first electrochemical demonstration of steam-sterilizable, storable, modular bioelectrode that undergoes reversible-thermal denaturation and retains electroactivity for protein based electrochemical applications.

| S-EPMC4610568 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data