Deoxyhemoglobin, structure

The quaternary structure adopted by the hybrids is the T form, where the metal-metal distance is 25 A the porphyrin planes are approximately parallel and the edge-edge distance is —20 A (Fig. 21). In the deoxyhemoglobin structure, the subunits of closest approach are aiP2- Since a,p ... 

Now, the C-terminal amino acids (the arginines in the a chains and the histidines in the P chains), which form hydrogen bonds that hold the chains in the "spring-loaded" deoxyhemoglobin structure, are attached directly to these tyrosines. Their motion causes the hydrogen bonds to break, not all at once but in a stepwise manner. It is the Fe(II) cations of the a chains that are oxygenated first, so it is their hydrogen bonds that break first. While intact. 

Figure 6-11. Representation of the sticky patch (A) on hemoglobin S and its "receptor" (A) on deoxyhemoglobin A and deoxyhemoglobin S. The complementary surfaces allow deoxyhemoglobin S to polymerize into a fibrous structure, but the presence of deoxyhemoglobin A will terminate the polymerization by failing to provide sticky patches. (Modified and reproduced, with permission, from Stryer L Biochemistry, 4th ed. Freeman, 1995.)...

Figure 4.4 Quaternary structure of deoxyhemoglobin tetramer visualized using Wavefunc-tion, Inc. Spartan 02 for Windows from PDB data deposited as 4HHB. See text for visualization details. Printed with permission of Wavefunction, Inc., Irvine, CA. (See color plate.)...

Figure A2.10 Protein structure human deoxyhemoglobin. Source Protein Data Bank,PDB ID lA3N.Tame J, Vallone B. http //www.rcsb.org/pdb/cgi/explore.cgi job= graphics pdbId=lA3N page=0 opt=show size=250 [accessed April 16, 2003]. Used with permission.)...

Fig. 9. Stereo drawing of proposed bicarbonate binding site between the two /3 chains of caiman deoxyhemoglobin. The central sign marks the dyad symmetry axis. Bicarbonates and their binding residues are underlined. Capital letters mark helical and interhelical segments (61). Residues are marked in sequential, rather than struaural notation. The following list gives the structural numbers with the sequential ones in parentheses Ser NAl (1) Pro NA2 (2) Phe NAS (3) Ser A1 (4) Ala A2 (5) His AS (6) Lys EF6 (82) Glu HCl (144) Tyr HC2 (145) His HC3 (146) all /3.

Figure 7.2 Quaternary structure of deoxyhemoglobin tetramer (PDB 4HHB). Visualized using The PyMOL Molecular Graphics System and ChemDraw Ultra, version 10.0. (Printed with permission of Delano Scientific, LLC and CambridgeSoft Corporation.)... 

Although the structure of deoxyhemoglobin resists loading of Oj, this resistance is overcome in the lungs by high PO2. 

Conditions in the peripheral tissues that stabilize the structure of deoxyhemoglobin promote dissociation of O2. 

Important Structural Features of the Active Sites of Metal Centres Deoxyhemoglobin, Cytochrome c, Vitamin Bi2 ... 

T," or taut, structure of deoxyhemoglobin "R," or relaxed, structure of oxyhemoglobin... 

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