Molecular oxygen migration through the xenon docking sites of human hemoglobin in the R-state.
A nanosecond laser flash-photolysis technique was used to study bimolecular and geminate molecular oxygen (O2) rebinding to tetrameric human hemoglobin and its isolated α and β chains in buffer solutions equilibrated with 1atm of air and up to 25atm of xenon. Xenon binding to the isolated α chains and to the α subunits within tetrameric hemoglobin was found to cause a decrease in the efficiency of O2 escape by a factor of ~1.30 and 3.3, respectively. A kinetic model for O2 dissociation, rebinding, and migration through two alternative pathways in the hemoglobin subunits was introduced and discussed. It was shown that, in the isolated α chains and α subunits within tetrameric hemoglobin, nearly one- and two-third escaping molecules of O2 leave the protein via xenon docking sites, respectively. The present experimental data support the idea that O2 molecule escapes from the β subunits mainly through the His(E7) gate, and show unambiguously that, in the α subunits, in addition to the direct E7 channel, there is at least one alternative escape route leading to the exterior via the xenon docking sites.
B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68 Nezavisimosti Ave, Minsk 220072, Belarus. Electronic address: lepeshkevich@imaph.bas-net.by.
Sergei V
SV
Lepeshkevich
Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, 5 Academician V.F. Kuprevich Street, Minsk 220141, Belarus. Electronic address: gilevich@iboch.bas-net.by.
Syargey N
SN
Gilevich
B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68 Nezavisimosti Ave, Minsk 220072, Belarus. Electronic address: marina@imaph.bas-net.by.
Marina V
MV
Parkhats
B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68 Nezavisimosti Ave, Minsk 220072, Belarus. Electronic address: bmd@imaph.bas-net.by.
Boris M
BM
Dzhagarov
D004229:Dithiothreitol / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry* / Q000302:isolation & purification; D006801:Humans; D007700:Kinetics; D008626:Mercuribenzoates / Q000737:chemistry; D062105:Molecular Docking Simulation; D010100:Oxygen / Q000737:chemistry*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry* / Q000302:isolation & purification; D013816:Thermodynamics; D014978:Xenon / Q000737:chemistry*
C043407:4-mercuribenzoate; D006454:Hemoglobins; D008626:Mercuribenzoates; D021122:Protein Subunits; D014978:Xenon; D010100:Oxygen; D004229:Dithiothreitol
Hemoglobin; Mercury; Molecular oxygen; Rebinding; Xenon