Haemoglobin structure

J21. de Jong, W. W. W., Chimpanzee foetal haemoglobin Structure and heterogeneity of the 7 chain. Biochim. Biophys. Acta 251, 217-226 (1971). 

A comparison of the deoxy- and oxy-haemoglobin structures reveals a number of important differences. Whereas in the T (deoxy) state the Fe atom is out of the haem plane, on oxygenation it moves into the plane of the now undomed porpyrin, pulling the proximal His F8 and the F-helix, to which it is attached, with it (Figure 13.6),... 

Figure Bl.2.10. Structure of the protohaeme unit found in haemoglobin and myoglobin.

Wliat are the structural dynamics of the tetramer as a whole The haemoglobin bound to O2 (Flb02) is not photoactive, so the CO adduct, FlbCO, is used instead. 

Scott T W and Friedman J M 1984 Tertiary-structure relaxation in haemoglobin—a transient Raman-study J. Am. Chem. Soc. 106 5677-87... 

Perutz, M.F., et al. Structure of haemoglobin. A three-dimensional Fourier synthesis at 5.5 A resolution, obtained by x-ray analysis. Nature 185 416-422, 1960. 

Fermi, G., Pemtz, M.F. Atlas of Molecular Structures in Biology. 2. Haemoglobin and Myoglobin. Oxford,... 

Beddell CR, Goodford PJ, Norrington FE, Wilkinson S, Wootton R. Compounds designed to fit a site of known structure in human haemoglobin. Br J Pharmacol 1976 57 201-9. 

Bettati S et al Allosteric mechanism of haemoglobin Rupture of salt-bridges raises the oxygen affinity of the T-structure. J Mol Biol 1998 281 581. 

FhuA and FepA will prove to be the reference structures for a large group of bacterial outer-membrane transporters that take up bacterial Fe3+-siderophores, Fe3+ released from host transferrin and lactoferrin, haem, and haem released from haemoglobin and haemopexin. It is assumed that all iron sources are transported... 

Even though the iron atoms are separated in haemoglobin by about 25 A, communication between them is still able to occur and this has been postulated to involve a trigger mechanism (Perutz, 1971). The trigger is the movement of the proximal histidine as dioxygen binds to (or is released from) the Fe(n) and results in interconversion between the T and R structures. This movement causes a conformational change which is transmitted through the protein to the other iron sites. X-ray studies indicate that relative shifts of up to 6 A at subunit interfaces occur between the T and R states (Perutz, 1978). 

A brief look at the contents page of any recent issue of the Journal of Molecular Biology (founded by John Kendrew, protein crystallographer and winner of the Nobel Prize for Chemistry together with Max Perutz for the 3-D structures of myoglobin and haemoglobin) will clearly establish that this is not so. 

Figure 13.5 (a) The structure of sperm whale myoglobin. (From Voet and Voet, 2004. Reproduced with permission from John Wiley Sons., Inc.) (b) The oxygen-binding curves of myoglobin and haemoglobin. (Reprinted with permission from Collman et al., 2004. Copyright (2004) American Chemical Society.)... 

The principles of ESR spectroscopy are very similar to NMR spectroscopy but the technique gives information about electron delocalizations rather than molecular structure and it enables the study of electron transfer reactions and the formation of paramagnetic intermediates in such reactions. In some situations, information regarding molecular structure can be obtained when suitable prosthetic groups are part of a molecule, e.g. FMN (flavin mononucleotide) in certain enzymes or the haem group in haemoglobin. Sometimes it is possible to attach suitable groups to molecules to enable their reactions to be monitored by ESR techniques. Such spin labels as they are called, are usually nitroxide radicals of the type... 

Globular proteins were much more difficult to prepare in an ordered form. In 1934, Bernal and Crowfoot (Hodgkin) found, that crystals were better preserved if they were kept in contact with their mother liquor sealed in thin-walled glass capillaries. By the early 1940s crystal classes and unit cell dimensions had been determined for insulin, horse haemoglobin, RNAase, pepsin, and chymotrypsin. Complete resolution of the structures required identification of the crystal axes and some knowledge of the amino acid sequence of the protein—requirements which could not be met until the 1950s. 

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