Table I. Dissociation constants and relative affinities (brackets) of a panel of Fyn SH2 variants for phosphopeptides representing different specificity classes.
| Peptide (Specificity Motif) | Fyn | Src | Grb2 | BRDG1 | V7 | V8 | V10 | V14 | V17 | V18 | V29 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| EPQpYENEEE (N2, p + 2N) | 0.7 ± 0.15 | 1.7 ± 0.34 | 0.8 ± 0.25 | NB | 0.8 ± 0.23 | 0.1 ± 0.097 (7) | 1.8 ± 0.48 | 0.3 ± 0.07 (2.3) | 2.5 ± 0.29 (0.3) | 0.7 ± 0.21 | 0.2 ± 0.08 (3.5) |
| QPEpYVNQADV (ErbB2-pY1139, p + 2N) | 5.7 ± 1.36 | 4.5 ± 1.56 | 0.4 ± 0.09 | NB | 6.3 ± 0.86 | 1.7 ± 0.28 (3.3) | 7.3 ± 2.66 | 4.2 ± 0.72 (1.3) | 24.5 ± 5.00 (0.2) | 6.8 ± 1.14 | 0.3 ± 0.04 (19) |
| EPQpYEEIEE (I3, p + 3I) | 0.6 ± 0.08 | 0.7 ± 0.13 | NB | NB | NB | 4.9 ± 1.08 (0.1) | 19.9 ± 4.54 | 0.1 ± 0.02 (6) | 4.1 ± 0.47 (0.1) | 1.0 ± 0.26 | 0.5 ± 0.11 (1.2) |
| NPDpYQQDFFP (EGFR-pY1172, p + 4) | 6.5 ± 1.36 | 5.0 ± 1.43 | 10.6 ± 2.84 | 27.2 ± 13.93 | 2.3 ± 0.38 | 23.7 ± 3.36 (0.2) | 4.8 ± 1.10 | 3.6 ± 0.52 (1.8) | 2.8 ± 0.33 (2.3) | 6.3 ± 0.71 | 2.1 ± 0.29 (3.1) |
| EPQpYEEELE (L4, p + 4L) | 2.5 ± 0.46 | 4.2 ± 1.04 | NB | 4.1 ± 0.51 | NB | 6.3 ± 1.77 (0.6) | 14.4 ± 2.66 | 1.0 ± 0.13 (2.5) | 0.3 ± 0.06 (8.3) | 1.3 ± 0.57 | 1.0 ± 0.18 (2.5) |
Notes: Dissociation constants (Kd, in μm, ±standard deviation) are derived from fluorescein polarization measurements (see also supplemental Fig. S7A–S7K). NB, no binding or binding too weak to determine the Kd of. All peptides were synthesized with an N-terminal spacer containing the sequence fluorescein-Ahx-Ahx-Ser-Gly-Gly, where Ahx denotes 6-aminohexanoic acid.