Conformational relevance of the β6Glu→Val mutation in the β subunits and in the β(1-55) and β(1-30) peptides of hemoglobin S

The β subunits of hemoglobin S showed a higher ellipticity than the β subunits of the hemoglobin A, both in the Soret and near ultraviolet regions. The apoderivatives of the β subunits of hemoglobin S showed a lower helical content and a larger amount of β conformation than the apoderivatives of the β subunits of hemoglobin A. The β(1-55) peptides and β(1-30) peptides from the β subunits of hemoglobin A and S have been separated and analyzed. The β(S)(1-55) peptide showed a higher content of β conformation and lower amount of α helix when compared to the β(A)(1-55) peptide aggregated with increasing ionic strength. The CD measurement showed that their secondary structure did not change upon a 10 fold dilution of the sample. Very little secondary structure was present in the β(S)(1-30) peptide, and the CD spectrum was very similar to that of the β(A)(1-30) peptide. No significant difference in aggregation was found between the β(S)(1-30) and β(A)(1-30) peptides.