Table 3.
Amino acid transport activities in Anabaena sp. strain PCC 7120 and mutant strains. BG11-grown cells were used in 10-min transport assays with 10 μM [14C]amino acid substrate as described in the Experimental Section. Activities are given in nmol (mg Chl)−1 per 10 min; the mean ± standard deviation of the mean (SE) from the number of measurements indicated in parenthesis is presented. The percentage of the wild-type activity is also given for the mutants. Differences between mutant and wild-type activities were assessed by the Student’s t test (P indicated in each case).
| Substrate | Transport activity (nmol [mg Chl]−1) | ||||||
|---|---|---|---|---|---|---|---|
| PCC 7120 | Mutant strain (inactivated ORF) | ||||||
| CSR6 (alr2536) | CSR3 (alr3429) | CSR1 (all0342) | |||||
| Mean ± SE (n) | Mean ± SE (n) | % (P) | Mean ± SE (n) | % (P) | Mean ± SE (n) | % (P) | |
| Basic | |||||||
| l-Arg | 125 ± 1.59 (25) | 115 ± 16.4 (3) | 92% (0.077) | 148 ± 6.60 (4) | 119% (0.187) | 195 ± 12.5 (3) | 156% (0.068) |
| l-Lys | 138 ± 1.55 (16) | 151 ± 3.92 (2) | 110% (0.167) | 163 ± 6.15 (3) | 118% (0.119) | 140 ± 8.40 (2) | 102% (0.882) |
| l-His | 88.0 ± 1.10 (16) | 71.7 ± 4.80 (3) | 81% (0.174) | 90.0 ± 4.94 (4) | 102% (0.863) | 132 ± 5.28 (3) | 150% (0.023) |
| Acidic | |||||||
| l-Asp | 37.3 ± 0.39 (27) | 33.5 ± 2.18 (3) | 90% (0.440) | 31.1 ± 1.67 (4) | 83% (0.170) | 38.8 ± 2.19 (4) | 104% (0.768) |
| l-Glu | 10.5 ± 0.12 (25) | 6.62 ± 0.70 (3) | 63% (0.061) | 10.2 ± 0.26 (4) | 97% (0.721) | 16.9 ± 1.56 (4) | 161% (0.130) |
| Neutral polar | |||||||
| l-Gln | 99.4 ± 0.90 (30) | 77.0 ± 6.89 (3) | 77% (0.189) | 99.3 ± 6.31 (4) | 100% (0.994) | 158 ± 6.48 (4) | 158% (0.014) |
| l-Ser | 218 ± 2.50 (10) | 195 ± 2.05 (2) | 90% (0.022) | 191 ± 9.37 (3) | 88% (0.237) | 239 ± 34.3 (3) | 110% (0.753) |
| Hydrophobic | |||||||
| l-Ala | 192 ± 1.09 (20) | 139 ± 13.4 (3) | 72% (0.145) | 203 ± 16.3 (4) | 105% (0.772) | 286 ± 6.03 (3) | 149% (0.004) |
| Gly | 200 ± 3.30 (15) | 107 ± 14.0 (3) | 54% (0.039) | 222 ± 8.84 (4) | 111% (0.337) | 252 ± 5.50 (3) | 126% (0.007) |
| l-Leu | 103 ± 0.99 (17) | 70.4 ± 5.34 (3) | 68% (0.051) | 117 ± 5.33 (4) | 113% (0.315) | 177 ± 12.0 (3) | 171% (0.067) |
| l-Pro | 135 ± 1.99 (16) | 82.8 ± 14.9 (3) | 61% (0.174) | 151 ± 10.0 (3) | 112% (0.449) | 198 ± 13.1 (4) | 147% (0.089) |
| l-Phe | 118 ± 1.87 (16) | 79.4 ± 1.78 (2) | 67% (<0.001) | 91.6 ± 7.79 (4) | 78% (0.197) | 109 ± 8.32 (3) | 92% (0.607) |