TABLE 3.
Regulation of expression of the Φ(aroF′-′lac), Φ(tyrP′-′lac), and Φ(tpl′-′lac) genes by mutant TyrR proteins
| lac fusiona | Growth mediumb | Sp. act. (Miller units) of β-galactosidase (mode of expression) of various lac fusions in the presence of mutant TyrR proteinsc
|
||||||
|---|---|---|---|---|---|---|---|---|
| E. coli (wild type) |
E. herbicola
|
None | ||||||
| Wild type | TyrRV67A | TyrRY72C | TyrRE201G | TyrRV67A Y72C E201G | ||||
| Φ(aroF′-′lac) | MM | 550 | 530 | 650 | 790 | 560 | 900 | 2,500 |
| MM+F | 230 (R2.4)d | 280 (R1.9) | 280 (R2.3) | 330 (R2.4) | 360 (R1.6) | 390 (R2.3) | 2,500 | |
| MM+Y | 29 (R19) | 31 (R17) | 43 (R15) | 42 (R19) | 33 (R17) | 62 (R15) | 2,600 | |
| Φ(tyrP′-′lac) | MM | 10 | 14 | 43 | 23 | 14 | 64 | 39 |
| MM+F | 30 (A3.0) | 19 (A1.4) | 26 (A0.6) | 26 (A1.1) | 26 (A1.9) | 42 (A0.7) | 38 | |
| MM+Y | 0.3 (R33) | 0.5 (R28) | 1.7 (R25) | 0.9 (R26) | 0.5 (R28) | 3.4 (R19) | 39 | |
| Φ(tpl′-′lac) | MM | 99 | 98 | 160 | 140 | 100 | 400 | 85 |
| MM+F | 410 (A4.1) | 260 (A2.6) | 1,000 (A6.3) | 340 (A2.4) | 260 (A2.6) | 1,200 (A3.0) | 85 | |
| MM+Y | 3,200 (A32) | 2,900 (A30) | 9,300 (A58) | 5,100 (A36) | 3,200 (A32) | 13,000 (A33) | 84 | |
The β-galactosidase activities of the Φ(aroF′-′lac) and Φ(tyrP′-′lac) genes were assayed in E. coli TK809, and the β-galactosidase activity of the Φ(tpl′-′lac) gene was assayed in E. coli TK596. The Φ(aroF′-′lac) and Φ(tyrP′-′lac) genes were on the pSC101-derived plasmid, and the Φ(tpl′-′lac) gene was on the mini-F plasmid.
E. coli strains were grown in M63-glucose MM or MM containing phenylalanine (MM+F) or tyrosine (MM+Y) as the coeffector of the TyrR protein at a final concentration of 1 mM.
E. coli cells with an appropriate lac fusion were transformed with the pACYC-derived plasmid (pTK479) (None) or pTK479 containing the tyrR allele of either E. coli or E. herbicola.
The values in parentheses represent the ratios of effector-mediated regulation. R and A indicate ratios of repression and activation, respectively. The ratio of repression was determined as the level of β-galactosidase in the cells grown in MM divided by that in the cells grown in the medium supplemented with a coeffector. The ratio of activation was determined as the level of β-galactosidase in the cells grown in the medium supplemented with a coeffector divided by that in the cells grown in MM.