Table I.
Yield of Ser during N-terminal sequencing of a phosphorylated and non-phosphorylated synthetic peptide
| Residue No. | Amino Acid | Yield of Ser
|
||
|---|---|---|---|---|
| Peak 1 | Peak 2 | Peak 3 | ||
| pmol | ||||
| 6 [24] | Arg | 5.6 | 3.8 | 4.3 |
| 7 [25] | Ser | 49 (100) | 54 (100) | 52 (100) |
| 8 [26] | Ser | 45 (92) | 37 (68) | 22 (44) |
| 9 [27] | Val | 6.7 | 9.2 | 7.8 |
| 10 [28] | Ser | 28 (57) | 7.8 (14) | 17 (33) |
| 11 [29] | Ile | 4.6 | 3.6 | 8.1 |
| 12 [30] | Val | 2.1 | 2.5 | 4.0 |
A synthetic peptide corresponding to A19 to M39 in BCA1p was phosphorylated with PKC, subjected to reverse-phase HPLC (Fig. 7), and the first 12 residues of peaks 1 to 3 were N-terminally sequenced. The yield of Ser-28 in radio-labeled peak 2 (underlined) was significantly lower than in peak 1 (non-radioactive), indicating that it was phosphorylated. Numbers in brackets correspond to the amino acid position in BCA1p. Numbers in parentheses are the percentage yield of Ser-26 and Ser-28 relative to the yield of Ser-25, which was set to 100%. Values for peak 3 have been multiplied with 1.7 to compensate for the lower amount of peptide subjected to sequencing.