Hemoglobin Perutz model

A model for the allosteric behavior of hemoglobin is based on recent observations that oxygen is accessible only to the heme groups of the a-chains when hemoglobin is in the T conformational state. Perutz has pointed out that the heme environment of /3-chains in the T state is virtually inaccessible because of steric hindrance by amino acid residues in the E helix. This hindrance dis-... 

Hemoglobin Is a large complex protein molecule the atomic model of oxyhemoglobin at 2.8 a resolution has been reported In 1968 by Perutz and coworkers, and a similar model of deoxy-hemoglobin In 1970 (1,2). The molecule Is a spheroid, approx-... 

Perutz has presented the most comprehensive allosteric model for the function of hemoglobin. It is of the symmetrical type and is presented in Figure 7.8. This model provides for the binding of 2,3-DPG by the T forms but not by the R... 

The model for the a helix received strong support when Max Perutz, working with hemoglobin and tilted fibers of keratin, observed a prominent meridional reflection at 1.5 A. This had been previously overlooked, and corresponds to the translation per amino acid residue along the polypeptide chain. The observation of such a meridional Bragg reflection is a good indication of the presence of an a helix. The existence of a helices was finally verified in the crystal structure of myoglobin. ... 

Figure 1.3.2 Model of hemoglobin deduced from x-ray diffraction studies. [After Perutz, M.F. 1964. The hemoglobin molecule. Set. Amer. 211(5), 64—76. Copyright 1964 by Scientific American, Inc. All rights reserved. With permission.)...

A photograph of Dr. Max Perutz s two angstrom-per-centi-meter x-ray diffraction model of hemoglobin is shown in Plate 3. Hemoglobin, the blood pigment that carries oxygen and makes the blood red, Is composed of four chains, two alpha globln chains... 

A different model of ox> gen-hemoglobin cooperativity arose after M Perutz et al. showed in the 1960s that hemoglobin has two different structures [9,10]. This model was due to J Monod, J Wyman, and P Changeux [11], and the mechanism is called allostery. We describe a simplified version of their model in the next section. 

Fig. 11. Models of hemoglobin subunits (according to Perutz). Two black and two white chains are so mounted that a hemoglobin molecule results when they are fitted together.

Fio. 12. Model of the hemoglobin molecule (according to Perutz). One white chain is removed for the sake of clarity. The lines are drawn in to show the course of the peptide chain (usually in the form of the ot-helix). The light disk in the black chain at right represents the porphyrin ring. 

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