Structure and evolution of artiodactyla haptoglobins

Evolutionary aspects of hemoglobin scavengers

With the evolution of fish, systems appeared for the disposal of the hemoglobin (Hb) that was inevitably released from erythrocytes. Thus, a plasma protein that bound free Hb with great affinity, haptoglobin (Hp), evolved from a protease of the innate immune system. In parallel, other proteins appeared (for example, hemopexin and alpha(1)-microglobulin), which bound and mediated the removal of free heme groups. Remarkably, Hp later disappeared in some vertebrate lineages, suggesting that it could also be disadvantageous. In the avian lineage, a soluble protein evolved, possibly from a scavenger receptor, which in some birds seems to have replaced Hp. Among mammals, multimeric forms of Hp appeared independently at two discrete times, suggesting that this form of the protein confers an advantage on the bearer, possibly by improving resistance to infection.

Purification of human haptoglobin 1-1, 2-1, and 2-2 using monoclonal antibody affinity chromatography

Similar to blood type, human plasma haptoglobin (Hp) is classified as 3 phenotypes: Hp 1-1, 2-1, or 2-2. The structural and functional relationship between the phenotypes, however, has not been studied in detail due to the complicated and difficult isolation procedures. This report provides a simple protocol that can be used to purify each Hp phenotype. Plasma was first passed through an affinity column coupled with a high affinity Hp monoclonal antibody. The bound material was washed with a buffer containing 0.2M NaCl and 0.02 M phosphate, pH 7.4, eluted at pH 11, and collected in tubes containing 1M Tris-HCl, pH 6.8. The crude Hp fraction was then chromatographed on a HPLC Superose 12 column in 0.05 M ammonium bicarbonate at a flow rate of 0.5 ml/min. The homogeneity of purified Hp 1-1, 2-1, or 2-2 was greater than 95% as judged by SDS-polyacrylamide gel electrophoresis. Essentially, each Hp isolated was not contaminated with hemoglobin and apolipoprotein A-I as that reported from the other methods, and was able to bind hemoglobin. Neuraminidase treatment demonstrated that the purified Hp possessed a carbohydrate moiety, while Western blot analysis confirmed alpha and beta chains corresponding to each Hp 1-1, 2-1, and 2-2 phenotype. The procedures described here represent a significant improvement in current purification methods for the isolation of Hp phenotypes. Circular dichroic spectra showed that the alpha-helical content of Hp 1-1 (29%) was higher than that of Hp 2-1 (22%), and 2-2 (21%). The structural difference with respect to its clinical relevance is discussed.

Development of an enzyme immuno assay for the determination of porcine haptoglobin in various body fluids: testing the significance of meat juice measurements for quality monitoring programs

Quantification of haptoglobin (Hp), an acute phase protein, in blood is presently discussed as being useful to monitor animal health. We developed an enzyme immuno assay (EIA) which is specific for porcine Hp, is not impaired by hemolytic samples and is sufficiently sensitive to be applied in meat juice. Hp was purified from porcine serum by affinity chromatography on hemoglobin Sepharose followed by gel filtration. A specific rabbit antiserum was obtained. In a competitive approach, biotinylated porcine Hp was used as tracer and incubated with Hp standard or sample in microtiter plates. The limit of detection was 0.02 mg/l, parallelism of sample dilutions was proven; recovery of Hp added to serum samples was 96.4 +/- 4.7%. The coefficients of intra and inter-assay variation were 3.3 (n=5) and 10.2% (n=16), respectively. Hp was reliably quantified in blood serum and plasma, whole blood, saliva and meat juice. For healthy pigs of different ages (4 weeks and 6 months), mean Hp concentrations of about 0.5-0.7 mg/ml were observed. To test the significance of Hp measurements in other matrices, samples were obtained from fattening pigs or from slaughter pigs. Blood serum or plasma was collected in parallel. In whole blood, Hp concentrations were about 40% lower than in plasma, but were closely related (n=24,r=0.85,P<0.001). Saliva Hp concentrations ranged between 0.3 and 3.0 microg/ml and were marginally related with blood plasma concentrations (n=93,r=0.35,P<0.001). From 106 hybrid slaughter pigs (100-110 kg) blood and muscle samples (diaphragmatic pillar, d.p.; m. brachiocephalicus, m.b.) were collected. Meat juice was obtained after freezing and thawing. Concentrations were 0.39+/-0.5 mg/ml in serum and 0.04+/-0.06 mg/ml in meat juice. Hp concentrations in blood were closely correlated with those in d.p. juice (P<0.001,r=0.750) and m.b. juice (P<0.001,r=0.776). In view of the many reports on Hp measurements being predictive for animal health even in the subclinical range, we conclude that Hp quantification in meat juice might be useful to assess meat quality at slaughter and further along the processing chain in terms of animal health.