Table II.
Proteolytic activity of thylakoids obtained from 6-d-old etiolated plants exposed to CL
| Exposure to CL | Endo LHCII
|
Exo LHCII Added | Endo + Exo LHCII Degraded | Thylakoid Protein: LHCII (w/w) | Percent LHCII Degraded
|
||
|---|---|---|---|---|---|---|---|
| Present | Degraded | Endo | Endo + Exo | ||||
| h | μg | mg−1 protein min−1 | |||||
| Nonsolubilized | |||||||
| 5 | 0.38 | 0.01 | 8 | 1.17 | 104.0 (4.7) | 2.21 | 11.74 |
| 10 | 0.96 | 0.33 | 8 | 5.16 | 40.7 (4.4) | 29.35 | 49.17 |
| 25 | 8.25 | 5.75 | 8 | 10.46 | 3.8 (1.9) | 73.17 | 67.58 |
| 50 | 15.00 | 5.00 | 8 | 9.60 | 1.7 (1.1) | 44.44 | 55.65 |
| 95 | 24.00 | 2.90 | 8 | 8.90 | 0.7 (0.5) | 25.17 | 57.94 |
| Solubilized | |||||||
| 25 | 8.25 | 7.24 | 8 | 15.20 | 3.8 (1.9) | 92.13 | 98.20 |
| 50 | 15.00 | 15.00 | 8 | 20.50 | 1.7 (1.1) | 133.33 | 118.84 |
| 95 | 24.00 | 24.00 | 8 | 31.00 | 0.7 (0.5) | 208.33 | 201.82 |
Total thylakoid protein (40 μg) was assayed for proteolytic activity after incubation for 30 min at 37°C before or after addition of 8 μg of exogenous (Exo) LHCII apoprotein. Whenever nonsolubilized thylakoids were used, the final TX-100 was 0.05%; solubilized samples had 0.5%. Final volume was 48 μL. Estimation of the exact amount of immunodetected endogenous (Endo) LHCII apoprotein is based on standard curves obtained from increasing known amounts of exogenous LHCII apoprotein immunoblotted on the same nitrocellulose membrane. Values for the ratio of thylakoid protein to LHCII are based on endogenous LHCII present. Values in parentheses are based on total LHCII apoprotein (endogenous + exogenous). Estimation of the rate is based on thylakoid protein after subtraction of the endogenous LHCII apoprotein.