9WW1
Oxy-bound rHb0.1WT beta homotetramer human hemoglobin
Summary for 9WW1
| Entry DOI | 10.2210/pdb9ww1/pdb |
| Descriptor | Hemoglobin subunit beta, PROTOPORPHYRIN IX CONTAINING FE, OXYGEN MOLECULE, ... (5 entities in total) |
| Functional Keywords | beta homotetramer, human hemoglobin, oxygen binding |
| Biological source | Homo sapiens (human) |
| Total number of polymer chains | 4 |
| Total formula weight | 66549.48 |
| Authors | |
| Primary citation | Yadav, K.,Verma, S.,Nag, A.,Kumar, P.,Kundu, S. Recombinant Hemoglobin rHb0.1 with Cross-Linked Alpha Subunits Preferentially Crystallizes in the beta 4 Oligomeric State, Potentially Driven by a beta G18(H116I) Mutation. Acs Omega, 11:27896-27912, 2026 Cited by PubMed Abstract: Hemoglobin rHb0.1 is a recombinant version of the red blood cell transport protein carrying cross-linked α-subunits (V1M and G15A) and β-subunit mutations (V1M, G16A, and H116I), which is used as a construct to develop recombinant hemoglobin-based oxygen carriers (rHBOCs). Spectroscopic studies revealed the altered stability of rHb0.1 compared to heterotetrameric (αβ) HbA. Heme dissociation kinetic analysis revealed nearly 2-fold faster rate constants ( and ) for rHb0.1 compared to HbA, with such differences necessitating structural studies for a greater insight into the variabilities. Here, we report the first crystal structure of the oxygen-bound β-rHb0.1 at 2.0 Å resolution, obtained from crystallization conditions designed for αβ rHb0.1, reflecting preferential crystallization of a preexisting β population in solution. The overall quaternary architecture in the oxy-bound state closely resembles ferric, deoxygenated, and carbomonoxy β HbA and liganded αβ R-state HbA. Unlike ferric β-HbA, the oxy-bound β-rHb0.1 structure prevents the formation of a disulfide bond between Cys112-(G14) residues of β1/β4 and β2/β3 subunits. A detailed comparison of the quaternary structures of oxy-bound (O-β) and ferric β (PDB: 6FQF) showed minimal conformational changes upon ligand binding to the β tetramer (RMSD across all 146 pairs: 0.714), demonstrating the remarkable structural conservation of β tetramers in different redox states. Lower expression of the di-α subunit compared to the β-subunit in solution seems to have triggered β homotetramer formation, as revealed by the crystal structure, with the H116I mutation in the β-subunit promoting this homotetramerization through extensive hydrophobic β-β interactions, offering insights into hemoglobin assembly, stability, and functional divergence from HbA. PubMed: 42719418DOI: 10.1021/acsomega.5c11376 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (2 Å) |
Structure validation
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