Figure 5.

Interpretation of the data in Table 1 showing regions of N-62 StAR that are protected from proteolysis at pH 4.0 and pH 8.0. (Top) The N-62 StAR construct has four Trp residues in the indicated positions and retains the 6 His-tag and 11 other amino-terminal aa (cross-hatched area); its total molecular mass is 26,933.8. (Middle) The truncated 16-kDa species resulting from limited trypsin digestion at pH 8.0 is shown with two possible carboxyl termini because resides 189–193 are not amenable to mass spectrometric analysis. Thus masses of either 16,027.0 or 16,641.8 are possible. (Bottom) The ≈6.5-kDa band isolated from pepsin digestion at pH 4 contains two partially overlapping peptides of 6,317.2 and 7,639.8, assuming the 189–193 peptide is retained.