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Journal ArticleDOI

Metal ion coordination in 'R' and 'T' state hybrid hemoglobins as revealed by optical, EPR and sulphhydryl reactivity studies

01 Mar 2005-Journal of Chemical Sciences (Springer India)-Vol. 117, Iss: 2, pp 85-97

Abstract: The sulphhydryl environment in various mixed-metal hybrid hemoglobins, viz. α2(Cu)-β2(FeCO), α2(FeCO)-β2(Cu), α2(Cu)-β2(Ni), α2(Ni)-β2(Cu), was studied by reacting them with the sulphhydryl reagent, 4,4′-dithiodipyridine (4-PDS). The reactivity was compared with that of HbCO, NiHb and CuHb. It is found that there exists a correlation between conformational change and metal ion environment, not only at the extreme R and T states but also the intermediate conformations. EPR examinations of these hybrids show that both in R state-[Cu(II)-Fe(II)] and T state-[Cu(II)-Ni(II)] hybrids at neutral pH and in the absence of IHP, CuPPIX, irrespective of the subunit in which it is present, has a mixed-metal ion environment: Species 1, a five-coordinated Cu2+ complex with strong proximal histidine bond and species 2, a four-coordinated complex without any covalent linkage with Ne F8-histidine.
Citations
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Journal ArticleDOI
TL;DR: The bond between N(epsilon) and Fe is fundamental to the structure-function relation in Hb, as the motion of this nitrogen triggers the vast transformation, which occurs in the whole molecule on attachment of NO.
Abstract: Subunit heterogeneity within a particular subunit in hemoglobin A have been explored with electron paramagnetic resonance spectroscopy using the nitrosyl hemes in Ni-Fe hybrid Hb under various solution conditions. Our previous studies on the crystal structure of NiHb demonstrated the presence of subunit heterogeneity within alpha-subunit. To further cross check this hypothesis, we made a hybrid Hb in which either the alpha- or beta-subunit contains iron, which alone can bind to NO. By this way dynamic exchange between penta- and hexa-coordinated forms within a subunit was confirmed. Upon the addition of inositol hexa phosphate (IHP) to these hybrids, R to T state transition is observed for [alpha(2)(Fe-NO)beta(2)(Ni)] but such a direct transformation is less marked in [alpha(2)(Ni)beta(2)(Fe-NO)]. Hence the bond between N(epsilon) and Fe is fundamental to the structure-function relation in Hb, as the motion of this nitrogen triggers the vast transformation, which occurs in the whole molecule on attachment of NO.

2 citations


References
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Journal ArticleDOI
A.Rossi Fanelli1, E. Antonini1, A. CaputoInstitutions (1)
TL;DR: The most important physicochemical constants of human globin and its coupling capacity for hematin are reported.
Abstract: A method of preparation of globin from human hemoglobin is reported. The protein so obtained has been submitted to different purity analyses such as electrophoresis, ultracentrifuge, diffusion, and heat-stability behaviour. The data obtained agree in demonstrating the high degree of purity of the protein. The most important physicochemical constants of human globin and its coupling capacity for hematin are reported.

577 citations


Journal ArticleDOI
Abstract: A new procedure is described using carboxymethyl cellulose and diethylaminoethyl cellulose columns for the preparation of native α and β chains from human hemoglobin. The chains appeared to be more stable than those obtained by earlier methods and permitted the preparation of modified chains containing meso- and deuterohemes. The kinetics of carbon monoxide binding was determined for proto-, meso-, and deutero-α and β chains by both stopped flow and flash photolysis methods. The kinetic properties of β—SH chains with protoheme are similar to those reported for hemoglobin H, and their rate of reaction with carbon monoxide is more than twice as great as that for α—SH chains.

340 citations


Journal ArticleDOI
Max F. Perutz1Institutions (1)
30 Jun 1972-Nature
TL;DR: Dr Perutz describes how spin changes that accompany reaction with ligands alter the oxygen affinity of the haems.
Abstract: Haem-haem interaction consists of a change of tension at the haems, caused by a transition between two alternative quaternary structures of the protein. Dr Perutz describes how spin changes that accompany reaction with ligands alter the oxygen affinity of the haems.

330 citations



Journal ArticleDOI
Abstract: Five- and six-coordinate nitrosyl hemes have been prepared and their infrared, electron paramagnetic resonance (EPR), and visible-Soret spectra compared with the corresponding spectra for nitrosyl hemoglobin A (Hba-NO) determined both in the presence and the absence of inositol hexaphosphate (IHP). The five- and six-coordinate NO complexes prepared from either dipyridine or pyridine carbonyl protoheme dimethyl ester had N-O stretch bands (nuno) near 1675 and 1625 cm-1, respectively. These frequencies are sensitive to change in solvent (nuno decreased as the dipole moment of the solvent increased) and, with six-coordinate species, to changes in trans ligand. However, these solvent and trans ligand effects were small compared with the difference (ca. 50 cm-11) between five- and six -coordinate species. The nature of the trans ligand affected the relative proportions of the two...

246 citations