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Biomedical subjects

M Rogard

Publications and source records attributed to M Rogard.

23 records · Page 2Linked to original sources
PubMed1977

Studies on hemoglobin tryptophanyl contact residues in the haptoglobin-hemoglobin complex.

Hemoglobin and apohemoglobin bind heptoglobin in the same molar ratio. Structural studies on haptoglobin-hemoglobin complex do not suggest any important structural changes in either protein upon binding. However, when apohemoglobin is bound to haptoglobin, a marked reduction in secondary structure, attributed to unfolding of globin chains, has been observed. Here we describe some properties of the haptoglobin-apohemoglobin (Hp-apoHb) complex, prepared by isoelectric focusing in the presence of an excess of haptoglobin. This complex does not exhibit the irreversibility of complexes obtained with hemoglobin in identical experimental conditions. The 'freezing' of the conformation of apohemoglobin upon binding to haptoglobin has been studied by fluorescence quenching experiments carried out in the presence of 8 M acrylamide. Changes in conformation of haptoglobin upon binding to apohemoglobin have been detected by titration of the exposed tryptophans using N-bromosuccinimide. Comparison of the additivity of exposed tryptophans in the complexes reveal that two tryptophans become inaccessible in the complex formation of haptoglobin with hemoglobin but not with apohemoglobin. These tryptophans, probably located on the alpha1beta2 contact interface of hemoglobin, have been tentatively identified as Trp-C3(37)beta.

Apoproteins↗
PubMed1976

Binding of human hemoglobin and its polypeptide chains with haptoglobin coupled to an agarose matrix.

The interactions of human haptoglobin covalently linked to agarose with human hemoglobin and with p-chloromercuribenzoic-acid-treated alpha and beta chains (alpha* and beta* chains) were studied by flow chromatography and equilibrium binding. The results indicate that in solid state, haptoglobin maintains the same binding characteristics as in solution, the order of binding affinities being: hemoglobin greater than alpha* chain greater than beta* chain. The study of the binding parameters of the alpha* chain shows an heterogeneity of binding sites on the haptoglobin and an average affinity constant Ka of 3.6 X 10(4)l/mol.

Binding Sites↗
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↗