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Results for “HAPTOGLOBINS”

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PubMed1990

Hemoglobin binding with haptoglobin: delineation of the haptoglobin binding site on the alpha-chain of human hemoglobin.

Previous studies from this laboratory employing a comprehensive synthetic overlapping peptide strategy showed that the alpha-chain of human hemoglobin (Hb) contains a single haptoglobin (HP) binding region residing within residues alpha 121-135. The present study describes a precise delineation of this Hp-binding site on the alpha-chain. Two overlapping peptides (alpha 111-125 and alpha 121-135) spanning this region and a panel of five peptides decreasing at the C-terminal from residue 135 by decrements of two residues (alpha 119-135, alpha 119-133, alpha 119-131, alpha 119-129, and alpha 119-127) were synthesized, purified, and characterized. Quantitative radiometric titration of 125I-labeled human HP (type 2-1) with adsorbents of each of these synthetic peptides showed that the peptide alpha 119-127 retained a Hp-binding activity equivalent to that of peptide alpha 121-135. This finding indicated that Lys-127 marked the C-terminal boundary of the binding site. Another panel of eight peptides was then synthesized, which had their C-terminus fixed at Lys-127 and increased at the N-terminus by one-residue increments from residue 122 up to residue 115 (alpha 122-127, alpha 121-127, alpha 120-127, alpha 119-127, alpha 118-127, alpha 117-127, alpha 116-127, and alpha 115-127). The binding of 125I-Hp to adsorbents of these peptides demonstrated that the N-terminal boundary of the site did not extend beyond Valine 121. It is, therefore, concluded that the Hp-binding site on the alpha-chain of human Hb comprises residues alpha 121-127.

Amino Acid Sequence↗

PubMed1995

Haptoglobin in Carnivora: a unique molecular structure in bear, cat and dog haptoglobins.

Haptoglobin (Hp), a hemoglobin-binding protein in plasma, consists of alpha and beta subunits and has a tetra-chain arrangement (beta-alpha-alpha-beta) connected by disulfide bridges in most mammals so far examined. Dog Hp has been reported to be unique compared with other Hps in respect that (1) the two alpha beta units are joined by a non-covalent interaction rather than a disulfide bridge and (2) the alpha chain has an oligosaccharide-binding sequence (Asn-X-Ser/Thr) and is glycosylated. To determine whether the unique structures of dog Hp are common in the Carnivora, we purified Hps from sera of bear and cat, and analyzed their subunit structure and partial amino acid sequences. The analyses by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, under both reducing and non-reducing conditions, revealed that bear and cat Hps have similar subunit arrangements to dog Hp, suggesting the absence of a disulfide bridge between two alpha chains. This was confirmed by amino acid sequence analysis of the alpha chains: that is, Cys15 participating in the inter-alpha chain disulfide bridge was replaced by Val in bear or Leu in cat and dog. Thus, the unique subunit arrangement of Hp reported in dog may be common in the Carnivora. In contrast to dog Hp, however, alpha chains of bear and cat Hps were found not to have the typical oligosaccharide binding sequence on their alpha chains and were not glycosylated.

Amino Acid Sequence↗

PubMed1995

A novel function of haptoglobin: haptoglobin-haemoglobin complex induces apoptosis of hepatocarcinomatous Hep 3B cells.

Haptoglobin-haemoglobin complex (Cx) showed a cytotoxic effect on the growth of Hep 3B (human hepatocellular carcinoma) cells, dose dependently. The antiproliferative effect of Cx on the multiplication of Hep 3B cells was augmented by the presence of prostaglandin (PG) D2. Antihuman Hb IgG abolished the effect of Cx, dose-dependently, which indicates that the antiproliferative effect of Cx really is exerted by Cx. Hep 3B cells treated with Cx showed the characteristic biochemical changes of apoptosis, such as DNA fragmentation which was blocked by pretreatment with cycloheximide, and the increase of transglutaminase expression. Thus, the antiproliferative effect of Cx against Hep 3B cells occurs via the typical apoptotic pathway.

Apoptosis↗

PubMed1976

Haptoglobin--haemoglobin interaction. Heterogeneity of the haptoglobin 1-1 molecule in its binding affinity for horse R/E-hemoglobin.

The formation of two different complexes when haptoglobin (Hp) and haemoglobin (Hb) are mixed in a 1:1 molar ratio is demonstrated by isoelectrofocusing. In these two complexes, the affinity of Hp for Hb is shown to be different, since Hb can be displaced only from one of the complexes, by a further addition of Hp. This is confirmed by a quantitative study of the reaction stoichiometry, when [Hp]/[Hb] = 1 and [Hp]/[Hb] greater than 1, which allows an evaluation of the amount of each complex formed. All these data cannot be explained other than by the existence of two forms of Hp molecule and a reaction scheme which fits these experiments is proposed.

Animals↗

PubMed2006

Association of haptoglobin levels with age, parasite density, and haptoglobin genotype in a malaria-endemic area of Gabon.

Haptoglobin (Hp) levels were investigated in relation to host genotype in a malaria-endemic area in Gabon. A cross-sectional study of 1-12-year-old children was conducted in the rainy season, a period of high malaria transmission, to examine this relationship. Variables that influenced Hp levels were Hp genotype, location, and age interacting with parasite density. At low parasite densities, there was a negative correlation between Hp levels and age. At higher densities, there was a positive correlation with age. This suggests that in the presence of greater parasite-induced hemolysis, older children are capable of increased production of Hp. Sickle cell trait and ABO blood group was not associated with Hp levels in this population.

Aging↗

PubMed2006

Haptoglobin levels are associated with haptoglobin genotype and alpha+ -Thalassemia in a malaria-endemic area.

Haptoglobin (Hp) is an acute phase protein that removes free hemoglobin (Hb) released during hemolysis. Hp has also been shown to be toxic for malaria parasites. alpha(+)-Thalassemia is a hemoglobinopathy that results in subclinical hemolytic anemia. alpha(+)-Thassemia homozygosity confers protection against severe malarial disease by an as yet unidentified mechanism. Hp levels were measured in a serial cross-sectional survey of children in Madang Province, Papua New Guinea (PNG). Hp levels were related to age, Hp genotype, Hb levels, parasitemia, splenomegaly, and alpha(+)-thalassemia genotype. Surprisingly, children who were homozygous for alpha(+) -thalassemia had significantly higher levels of Hp than did heterozygotes, after controlling for relevant confounders. We suggest that this is the result of either reduced mean cell Hb associated with alpha(+) -thalassemia homozygosity or an elevated IL-6-dependent acute phase response.

Adolescent↗

PubMed1978

Studies on the structure of haptoglobin and the haptoglobin-haemoglobin complex by spin and fluorescence labelling.

Human haptoglobin (Hp) of the 1-1 type incorporated one spin or fluorescence marker per molecule; the markers were found in the beta chain. Formation of the complex between spin-labelled Hp and haemoglobin or antibody caused conformational changes in the Hp molecular, evidenced by increased participation in the electron paramagnetic resonance spectrum of the component bound with the slowly rotating marker. From fluorescence-labelled Hp, the beta chain was isolated and cleaved by CNBr; only in one of the obtained peptides, one out of 4 histidine residues was modified with the marker.

Cyanogen Bromide↗

PubMed1981

Haptoglobin polymorphism among Saharian and West African groups. Haptoglobin phenotype determination by radioimmunoelectrophoresis on Hp O samples.

The haptoglobin (Hp) polymorphism is investigated in 11 African groups living in an area from the Algerian Sahara to Central Africa. More than 4,000 samples were examined. In the Saharian samples, the Hp1 gene frequency is higher than in any other African group. From north to south, a decrease in the Hp1 gene frequency is observed; in the Pygmy sample only, this frequency is lower than the frequency of the Hp2 gene. By means of a sensitive radioimmunoelectrophoresis, the presence of a residual Hp in Hp O sera in which the Hp polymorphism can also be determined can be revealed. Absence of Hp 1-1 and significant excess of Hp 2-2 individuals were observed. More Hp 2-1M phenotypes were detected in the Hp O population than in the non-Hp O population examined. In the Hp O samples, the influence of the phenotype distribution on the Hp gene frequencies is discussed. The heavy polymers of the Hp related to the presence of the alpha 2 chain (Hp2 gene product) are involved only in the biological mechanisms responsible for the presence of Hp O and Hp 2-1 M phenotypes among African groups.

Africa, Central↗

PubMed1996

Validation of human haptoglobin immunoturbidimetric assay for detection of haptoglobin in equine and canine serum and plasma.

The Incstar(R) SPQ II human haptoglobin (Hpt) (Incstar Corporation, Stillwater, MN) immunoturbidimetric assay was validated for the determination of serum and plasma Hpt concentrations in dogs and horses. The anti-human Hpt antiserum supplied with the assay, displayed monospecificity to both dog and horse serum Hpt by immunoelectrophoresis and Western blotting techniques. The automated immunoturbidimetric assay results correlated well with the cyanmethemoglobin binding assay (r=0.953 for canine serum and r=0.941 for equine serum), and had excellent precision at both high and low serum Hpt concentrations (within run and between run coefficients of variation near or less than 5%). The assay was linear in both species by serial dilution of pooled-high serum with pooled-low serum, saline and with Hpt-free serum. Interference from hemolysis (> 25 mg/dl hemoglobin) and lipemia greater than 100 mg/dl caused a false decrease and false increase respectively in Hpt yield with the immunoturbidimetric assay. The anti-Hpt antibody supplied with the assay kit, once diluted with polymer diluent and stored at 4 degrees C, was stable for up to 6 days and gave consistent results.

Journal Article↗

PubMed1965