Table 3.
Physical properties of ATCase holoenzyme variants containing circularly permuted c chains
| Variant | s (S) | Δs/sa,b (%) | Tma,c (°C) | ΔTmd (°C) | ΔA290-285e (mg • cm • mL−1 |
| ATCasewt | 11.5 | −2.9 | 64.1 | +0.6 | 0.014 |
| ATCaseH6 | 11.6 | −2.6 | 63.5 | +0.0 | 0.011 |
| A32/A32-NKVN | 11.6 | −2.0 | 62.5 | −1.0 | 0.011 |
| Q137/S131 | 11.4 | −0.0 | 59.8 | −3.7 | 0.000 |
| Q137/T136 | 11.5 | n.d.f | 49.7 | −13.8 | 0.001 |
| Q137/T136-HKVN | 11.6 | n.d.f | 49.6 | −13.9 | 0.001 |
| V169/S171-LR | 11.4 | +0.2 | 62.8 | −0.7 | 0.001 |
| H170/T173-HKVN | 11.5 | −0.1 | 61.7 | −1.8 | 0.001 |
| I215/E217-VR | 11.4 | −2.3 | 59.9 | −3.6 | 0.008 |
| R54/T53-LR | 11.4 | +0.3 | 64.5 | +1.0 | n.d.f |
| R56/R54-IR | 11.3 | −0.2 | 59.4 | −4.1 | n.d.f |
a Average of two or more experiments performed on two independent protein preparations.
b Percent change in the sedimentation coefficient promoted by the bisubstrate analog PALA.
cTm is the midpoint of the unfolding transition in differential scanning calorimetry experiments.
d Difference in Tm relative to ATCaseH6.
e ΔA290-285 is the absorbance difference between the maximum at 290 nm and the minimum at 285 nm for protein containing PALA (4 PALA/active site) versus without PALA.
f Not determined.