Table 1. Site-directed spin label mutants of GRP1 PH domain and their measured parameters.
| PH Domain 1 | Ki ± SEM (µM) | EPR Spectral Change 2 | Π (O2) ± SEM | Π (Ni) ± SEM | ϕ ± SEM |
| Wild-type | 0.81±0.05 | NA | NA | NA | NA |
| Cysless | 0.97±0.20 | NA | NA | NA | NA |
| V278R1 Lβ1-β2 | 1.20±0.08 | ++ | 0.25±0.01 | 0.17±0.02 | 0.31±0.02 |
| T280R1 Lβ1-β2 | 0.70±0.16 | ++ | 0.27±0.05 | 0.53±0.03 | −0.68±0.03 |
| K282R1 β2 | 0.97±0.06 | − | 0.26±0.03 | 0.19±0.01 | 0.30±0.01 |
| Y298R1 Lβ3-β4 | 1.37±0.05 | + | 0.38±0.02 | 1.18±1.11 | −1.15±0.01 |
| T300R1 Lβ3-β4 | 1.33±0.01 | − | 0.21±0.04 | 1.00±0.10 | −1.57±0.01 |
| K302R1 Lβ3-β4 | 0.63±0.16 | + | 0.22±0.01 | 1.12±0.04 | −1.66±0.02 |
| E303R1 Lβ3-β4 | 0.74±0.27 | + | 0.21±0.04 | 0.66±0.03 | −1.19±0.01 |
| I307R1 β4 | 1.01±0.28 | + | 0.17±0.01 | 0.77±0.09 | −1.50±0.01 |
| E319R1 Lβ5-β6 | 0.87±0.25 | + | 0.17±0.01 | 0.81±0.24 | −1.52±0.01 |
| R322R1 Lβ5-β6 | 1.69±0.09 | ++ | 0.31±0.03 | 0.29±0.04 | 0.10±0.02 |
| K323R1 Lβ5-β6 | 0.93±0.29 | + | 0.22±0.06 | 0.78±0.06 | −1.29±0.03 |
| N325R1 β6 | 1.34±0.02 | − | 0.25±0.01 | 0.93±0.20 | −1.30±0.03 |
| A346R1 Lβi1-βi2 | 1.16±0.01 | ++ | 0.24±0.01 | 0.56±0.05 | −0.87±0.01 |
| D347R1 Lβi1-βi2 | 1.31±0.01 | ++ | 0.24±0.08 | 0.29±0.05 | −0.23±0.01 |
| V351R1 βi2 | 0.98±0.18 | + | 0.21±0.01 | 1.00±0.08 | −1.58±0.02 |
| E352R1 βi2 | 1.17±0.11 | + | 0.28±0.06 | 0.80±0.04 | −1.09±0.03 |
| S364R1 Lβ7-α1 | 1.02±0.09 | − | 0.22±0.04 | 1.35±0.03 | −1.85±0.01 |
| K373R1 α1 | 0.64±0.02 | + | 0.32±0.02 | 1.15±0.17 | −1.29±0.01 |
1
For spin-labeled mutants (R1), the indicated residue in the Cysless PH domain is changed to Cys and labeled with MTSSL. Also indicated is the secondary structure element in which each spin label is located.
2
The qualitative ranking of spectral changes in Figure 4 utilizes three categories: large change (++), detectable change (+) and no detectable change (−).