TABLE 3.
Production levels and specific activities of single-cysteine variants relative to those of cysteineless AspT
| Variant | Production (%)a | Sp act (%)b | Location |
|---|---|---|---|
| Cysteineless AspT | 100.0 | 100.0 | |
| A3C | 98.7 ± 2.1 | 101.6 ± 1.5 | Periplasm |
| S33C | 108.9 ± 3.2 | 90.8 ± 9.2 | Cytoplasm |
| T59C | 81.2 ± 8.3 | 60.2 ± 1.9 | Periplasm |
| A90C | 100.7 ± 0.7 | 70.5 ± 5.1 | Cytoplasm |
| L151C | 98.6 ± 0.4 | 106.6 ± 1.3 | Periplasm |
| S156C | 63.2 ± 1.3 | 261.2 ± 17.8 | Periplasm |
| P160C | 85.6 ± 2.2 | 66.6 ± 1.1 | Periplasm |
| M182C | 86.0 ± 1.4 | 96.5 ± 2.3 | Cytoplasm |
| M186C | 120.6 ± 4.3 | 33.3 ± 0.7 | Cytoplasm |
| L190C | 95.0 ± 1.8 | 34.4 ± 0.4 | Cytoplasm |
| A194C | 91.1 ± 1.5 | 51.8 ± 4.9 | Cytoplasm |
| S291C | 105.4 ± 1.7 | 78.8 ± 2.2 | Cytoplasm |
| S351C | 98.2 ± 0.5 | 86.0 ± 3.3 | Cytoplasm |
| S386C | 94.8 ± 1.3 | 127.5 ± 6.7 | Periplasm |
| Y408C | 48.4 ± 2.5 | 140.0 ± 4.3 | Cytoplasm |
| H412C | 129.5 ± 2.3 | 49.3 ± 0.9 | Cytoplasm |
| S421C | 84.7 ± 1.5 | 121.4 ± 6.8 | Cytoplasm |
| S448C | 99.1 ± 1.3 | 69.4 ± 4.0 | Periplasm |
| T472C | 109.7 ± 0.6 | 42.5 ± 2.7 | Cytoplasm |
| M480C | 88.2 ± 0.5 | 59.5 ± 2.9 | Cytoplasm |
| S486C | 108.1 ± 1.7 | 111.6 ± 2.9 | Cytoplasm |
| S510C | 94.4 ± 1.7 | 49.8 ± 2.9 | Cytoplasm |
| S543C | 84.3 ± 2.8 | 110.4 ± 11.0 | Periplasm |
a
Production is expressed relative to that of the cysteineless parent. The values are means ± standard deviations.
b
The initial rates of l-[2,3-3H]aspartate transport, normalized for the levels of AspT production, are expressed relative to the rate for the cysteineless parent, whose activity was 4.24 nmol min−1 mg of protein−1. The data are the means ± standard deviations for three independent trials. For each single-cysteine variant, the same amount of protein was used for reconstitution in l-aspartate-loaded proteoliposomes.