Table I.
Membrane association of GUS-tagged AtCPK2 proteins in transgenic plants
| Protein Expressed in Transgenic Plants | No. of Independent Experiments | No. of Independent Transgenic Lines | GUS-Specific Activity in Membrane Fractiona | Membrane-Associated GUS Activityb |
|---|---|---|---|---|
| % | ||||
| CPK2-GUS | 7 | 3 | 67.1–154.2 | 40 ± 2.3 |
| CPK2(G2A)-GUS | 7 | 3 | 37.5–76.6 | 18 ± 1.7 |
| CPK2-PR | 4 | 2 | 5.2–8.3 | 46 ± 2 |
After low-speed centrifugation, plant extracts were ultracentrifuged to pellet microsomes. The supernatant after ultracentrifugation contains primarily soluble proteins, whereas the pellet contains primarily membrane-bound proteins. Both the supernatant and the pellet were assayed fluorimetrically for GUS enzymatic activity.
a
Specific activity units are nmol methylumbelliferone produced min−1 mg protein−1.
b
Values were calculated from the total enzyme activity data and are presented as mean ± sd.