TABLE 1.
Characterization of amino acid substitutions at position L111
| Substitutiona | Sp act (nmol of product formed/min/mg of protein)b
|
||
|---|---|---|---|
| Urease | Histidase | GDH | |
| No NAC | 17 | 45 | 875 |
| Wild type | 857 | 326 | 28 |
| L111P | 597 | 209 | 335 |
| L111K | 1,080 | 239 | 431 |
| L111R | 959 | 219 | 330 |
| L111Q | 1,326 | 265 | 365 |
| L111T | 1,052 | 211 | 253 |
| L111D | 748 | 233 | 282 |
| L111E | 810 | 253 | 262 |
| L111N | 825 | 233 | 215 |
| L111G | 778 | 237 | 170 |
| L111S | 745 | 233 | 163 |
| L111A | 806 | 222 | 73 |
| L111H | 756 | 250 | 90 |
| L111C | 708 | 305 | 31 |
| L111I | 735 | 409 | 28 |
| L111M | 762 | 294 | 31 |
| L111V | 722 | 302 | 31 |
| L111F | 856 | 343 | 18 |
| L111W | 563 | 268 | 37 |
| L111Y | 17 | 60 | 695 |
a
All mutants were carried as cloned fragments in pCB1041. No NAC, pCB1041; Wild type, pCB1051. The background strain was KC4598 (hutC515 nac-204::λplac Mu53 srl-7012::Tn5-131).
b
Cells were grown in W4 minimal salts (18) supplemented with glucose (0.4%), ammonium sulfate (0.2%), glutamine (0.2%), 2 μM nickel sulfate, and 100 μg of ampicillin per ml. Assay values are reported as specific activities and are the mean of at least three independent experiments in which the standard error was <15% of the mean.