Dataset Information

Sickle Cell Hemoglobin with Mutation at ?His-50 Has Improved Solubility.

ABSTRACT: The unliganded tetrameric Hb S has axial and lateral contacts with neighbors and can polymerize in solution. Novel recombinants of Hb S with single amino acid substitutions at the putative axial (recombinant Hb (rHb) (?E6V/?H20R) and rHb (?E6V/?H20Q)) or lateral (rHb (?E6V/?H50Q)) or double amino acid substitutions at both the putative axial and lateral (rHb (?E6V/?H20R/?H50Q) and rHb (?E6V/?H20Q/?H50Q)) contact sites were expressed in Escherichia coli and purified for structural and functional studies. The (1)H NMR spectra of the CO and deoxy forms of these mutants indicate that substitutions at either ?His-20 or ?His-50 do not change the subunit interfaces or the heme pockets of the proteins. The double mutants show only slight structural alteration in the ?-heme pockets. All mutants have similar cooperativity (n50), alkaline Bohr effect, and autoxidation rate as Hb S. The oxygen binding affinity (P50) of the single mutants is comparable with that of Hb S. The double mutants bind oxygen with slightly higher affinity than Hb S under the acidic conditions. In high salt, rHb (?E6V/?H20R) is the only mutant that has a shorter delay time of polymerization and forms polymers more readily than Hb S with a dextran-Csat value of 1.86 ± 0.20 g/dl. Hb S, rHb (?E6V/?H20Q), rHb (?E6V/?H50Q), rHb (?E6V/?H20R/?H50Q), and rHb (?E6V/?H20Q/?H50Q) have dextran-Csat values of 2.95 ± 0.10, 3.04 ± 0.17, 11.78 ± 0.59, 7.11 ± 0.66, and 10.89 ± 0.83 g/dl, respectively. rHb (?E6V/?H20Q/?H50Q) is even more stable than Hb S under elevated temperature (60 °C).

SUBMITTER: Tam MF

PROVIDER: S-EPMC4571898 | biostudies-literature | 2015 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Sickle Cell Hemoglobin with Mutation at αHis-50 Has Improved Solubility.

Tam Ming F MF Tam Tsuey Chyi S TC Simplaceanu Virgil V Ho Nancy T NT Zou Ming M Ho Chien C

The Journal of biological chemistry 20150716 35

The unliganded tetrameric Hb S has axial and lateral contacts with neighbors and can polymerize in solution. Novel recombinants of Hb S with single amino acid substitutions at the putative axial (recombinant Hb (rHb) (βE6V/αH20R) and rHb (βE6V/αH20Q)) or lateral (rHb (βE6V/αH50Q)) or double amino acid substitutions at both the putative axial and lateral (rHb (βE6V/αH20R/αH50Q) and rHb (βE6V/αH20Q/αH50Q)) contact sites were expressed in Escherichia coli and purified for structural and functional ...[more]

PMID: 26187468

Similar Datasets

Project description:Intravascular hemolysis and hemoglobinuria are associated with sickle cell nephropathy. ApoL1 is involved in cell-free hemoglobin scavenging through association with haptoglobin-related protein. APOL1 G1/G2 variants are the strongest genetic predictors of kidney disease in the general African-American population. A single report associated APOL1 G1/G2 with sickle cell nephropathy. In 221 patients with sickle cell disease at the University of Illinois at Chicago, we replicated the finding of an association of APOL1 G1/G2 with proteinuria, specifically with urine albumin concentration (?=1.1, P=0.003), observed an even stronger association with hemoglobinuria (OR=2.5, P=4.3×10(-6)), and also replicated the finding of an association with hemoglobinuria in 487 patients from the Walk-Treatment of Pulmonary Hypertension and Sickle cell Disease with Sildenafil Therapy study (OR=2.6, P=0.003). In 25 University of Illinois sickle cell disease patients, concentrations of urine kidney injury molecule-1 correlated with urine cell-free hemoglobin concentrations (r=0.59, P=0.002). Exposing human proximal tubular cells to increasing cell-free hemoglobin led to increasing concentrations of supernatant kidney injury molecule-1 (P=0.01), reduced viability (P=0.01) and induction of HMOX1 and SOD2. HMOX1 rs743811 associated with chronic kidney disease stage (OR=3.0, P=0.0001) in the University of Illinois cohort and end-stage renal disease (OR=10.0, P=0.0003) in the Walk-Treatment of Pulmonary Hypertension and Sickle cell Disease with Sildenafil Therapy cohort. Longer HMOX1 GT-tandem repeats (>25) were associated with lower estimated glomerular filtration rate in the University of Illinois cohort (P=0.01). Our findings point to an association of APOL1 G1/G2 with kidney disease in sickle cell disease, possibly through increased risk of hemoglobinuria, and associations of HMOX1 variants with kidney disease, possibly through reduced protection of the kidney from hemoglobin-mediated toxicity.

Project description:Hemoglobin A1c (HbA1c) reflects past glucose concentrations, but this relationship may differ between those with sickle cell trait (SCT) and those without it.To evaluate the association between SCT and HbA1c for given levels of fasting or 2-hour glucose levels among African Americans.Retrospective cohort study using data collected from 7938 participants in 2 community-based cohorts, the Coronary Artery Risk Development in Young Adults (CARDIA) study and the Jackson Heart Study (JHS). From the CARDIA study, 2637 patients contributed a maximum of 2 visits (2005-2011); from the JHS, 5301 participants contributed a maximum of 3 visits (2000-2013). All visits were scheduled at approximately 5-year intervals. Participants without SCT data, those without any concurrent HbA1c and glucose measurements, and those with hemoglobin variants HbSS, HbCC, or HbAC were excluded. Analysis of the primary outcome was conducted using generalized estimating equations (GEE) to examine the association of SCT with HbA1c levels, controlling for fasting or 2-hour glucose measures.Presence of SCT.Hemoglobin A1c stratified by the presence or absence of SCT was the primary outcome measure.The analytic sample included 4620 participants (mean age, 52.3 [SD, 11.8] years; 2835 women [61.3%]; 367 [7.9%] with SCT) with 9062 concurrent measures of fasting glucose and HbA1c levels. In unadjusted GEE analyses, for a given fasting glucose, HbA1c values were statistically significantly lower in those with (5.72%) vs those without (6.01%) SCT (mean HbA1c difference, -0.29%; 95% CI, -0.35% to -0.23%). Findings were similar in models adjusted for key risk factors and in analyses using 2001 concurrent measures of 2-hour glucose and HbA1c concentration for those with SCT (mean, 5.35%) vs those without SCT (mean, 5.65%) for a mean HbA1c difference of -0.30% (95% CI, -0.39% to -0.21%). The HbA1c difference by SCT was greater at higher fasting (P?=?.02 for interaction) and 2-hour (P?=?.03) glucose concentrations. The prevalence of prediabetes and diabetes was statistically significantly lower among participants with SCT when defined using HbA1c values (29.2% vs 48.6% for prediabetes and 3.8% vs 7.3% for diabetes in 572 observations from participants with SCT and 6877 observations from participants without SCT; P<.001 for both comparisons).Among African Americans from 2 large, well-established cohorts, participants with SCT had lower levels of HbA1c at any given concentration of fasting or 2-hour glucose compared with participants without SCT. These findings suggest that HbA1c may systematically underestimate past glycemia in black patients with SCT and may require further evaluation.

Dataset Information

Sickle Cell Hemoglobin with Mutation at ?His-50 Has Improved Solubility.

Publications

Sickle Cell Hemoglobin with Mutation at αHis-50 Has Improved Solubility.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets