Binding of a spin-labeled phenylalanine analog to sickle hemoglobin: EPR and NMR studies.
We have synthesized a spin-label analog of phenylalanine as a competitive inhibitor probe of the sickle hemoglobin aggregation process. Sickle hemoglobin gelation measurements indicate that the spin-label phenylalanine analog is a potent inhibitor of deoxy sickle hemoglobin aggregation. We have also used spin label EPR and high-resolution proton NMR to study the interaction of the phenylalanine analog with hemoglobin, and find that the kinetic off-rate is comparable to, or slower than the hemoglobin rotational rate (i.e., greater than or equal to 10(8) s-1), and that at least one, and perhaps two significant localized interaction region(s) exist within a few angstroms of the beta chain N- and C-termini. Correlation with other known structural information suggests that the observed interaction sites may be relevant to the mechanism for inhibition of sickle hemoglobin aggregation.
D001665:Binding Sites; D002263:Carboxyhemoglobin / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006451:Hemoglobin, Sickle / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D010649:Phenylalanine / Q000031:analogs & derivatives* / Q000378:metabolism; D011487:Protein Conformation; D012995:Solubility; D013113:Spin Labels; D013329:Structure-Activity Relationship
D006451:Hemoglobin, Sickle; D006454:Hemoglobins; D013113:Spin Labels; D010649:Phenylalanine; D002263:Carboxyhemoglobin