6otw | pdb_00006otw

Crystallographic Structure of (HbII-HbIII)-O2 from Lucina pectinata at pH 5.0

spinqualitylabelsall models 6otw, resolution 2.45Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6otw is a 2 chain structure with sequence from Lucina pectinata. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: HEM Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed Lucina pectinata live in high concentrations of hydrogen sulfide (H2S) and contains one hemoglobin, Hemoglobin I (HbI), transporting H2S and two hemoglobins, Hemoglobin II (HbII) and Hemoglobin (HbIII), transferring dioxygen to symbionts. HbII and HbIII contain B10 tyrosine (Tyr) and E7 glutamine (Gln) in the heme pocket generating an efficient hydrogen bonding network with the (HbII-HbIII)-O2 species, leading to very low ligand dissociation rates. The results indicate that the oxy-hemeprotein is susceptible to pH from 4 to 9, at acidic conditions, and as a function of the potassium ferricyanide concentration, 100% of the met-aquo derivative is produced. Without a strong oxidant, pH 5 generates a small concentration of the met-aquo complex. The process is accelerated by the presence of salts, as indicated by the crystallization structures and UV-Vis spectra. The results suggest that acidic pH generates conformational changes associated with B10 and E7 heme pocket amino acids, weakening the (HbII-HbIII)-O2 hydrogen bond network. The observation is supported by X-ray crystallography, since at pH 4 and 5, the heme-Fe tends to oxidize, while at pH 7, the oxy-heterodimer is present. Conformational changes also are observed at higher pH by the presence of a 605 nm transition associated with the iron heme-Tyr interaction. Therefore, pH is one crucial factor regulating the (HbII-HbIII)-O2 complex hydrogen-bonding network. Thus, it can be proposed that the hydrogen bonding adjustments between the heme bound O2 and the Tyr and Gln amino acids contribute to oxygen dissociation from the (HbII-HbIII)-O2 system. Lucina pectinata oxyhemoglobin (II-III) heterodimer pH susceptibility.,Marchany-Rivera D, Smith CA, Rodriguez-Perez JD, Lopez-Garriga J J Inorg Biochem. 2020 Mar 7;207:111055. doi: 10.1016/j.jinorgbio.2020.111055. PMID:32217352 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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