[Localization of pyridoxal-5-phosphate, covalently bound with human hemoglobin. Spectrofluorimetric studies].
Human apohemoglobin tryptophan residues were localized in the regions of the protein globule with restricted mobility. By the method of dynamic quenching of phosphopyridoxyl chromophore fluorescence, the heterogeneity of pyridoxal-5-phosphate molecules covalently bound to the human hemoglobin molecules was determined from the accessibility to solvent. The first four pyridoxal-5-phosphate molecules are localized in the hydrophobic regions of the hemoglobin molecule; at the same time, they have a high mobility. One of these molecules is situated at the site inaccessible to the solvent, which coincides with the anion-binding center of the oxyhemoglobin molecule. The next pyridoxal-5-phosphate molecules modify the surface amino groups of the protein. In the apohemoglobin molecule, the pyridoxal-5-phosphate binding sites are more exposed to the solvent, as compared to hemoglobin. In the hemoglobin molecule modified by pyridoxal-5-phosphate, an effective electron excitation energy transfer from tryptophan residues to phosphopyridoxyl chromophores occurs. The effective distances between tryptophanyls of single subunits of hemoglobin and the covalently bound pyridoxal-5-phosphate molecule were estimated to be 19 A for the alpha-subunit and 17 A for the beta-subunit.
Zavodnik
I B
IB
Institute of Biochemistry, Belarussian Academy of Sciences, Grodno, Belarus.
Konovalova
N V
NV
Stepuro
I I
II
D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D011485:Protein Binding; D011732:Pyridoxal Phosphate / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry
D006454:Hemoglobins; D011732:Pyridoxal Phosphate; D014364:Tryptophan
Lokalizatsiia piridoksal'-5-fosfata, kovalentno sviazannogo s gemoglobinom cheloveka. Spektrofluorimetricheskie issledovaniia.