TABLE 3.
Suppression of btuB L8P and V10P mutations by Cys substitutions in TonBa
| Plasmid or plasmid-encoded substitution | Concn of CN-Cbl for maximal growth (nM) of strain carrying:
|
|||
|---|---|---|---|---|
| tonBb |
btuBc
|
|||
| pBtuB+ | pL8P | pV10P | ||
| pSU19 | >5,000 | 0.5 | 5,000 | 5,000 |
| pTonB | 0.5 | 0.5 | 1,000 | 5,000 |
| pExbBD | >5,000 | 0.5 | 5,000 | 5,000 |
| pTonBExbBD | 0.5 | 0.5 | 1,000 | 5,000 |
| C18A | 0.5 | 0.5 | 500 | 5,000 |
| N159C | 0.5 | 0.5 | 500 | 50 |
| Q160C | 0.5 | 0.5 | 0.5 | 0.5 |
| P161C | 0.5 | 0.5 | 1,000 | 5,000 |
| Q162C | 0.5 | 0.5 | 50 | 50 |
| Y163C | 0.5 | 0.5 | 1,000 | 5,000 |
| P164C | 0.5 | 0.5 | 500 | 5,000 |
a
Concentrations of CN-Cbl affording colony sizes comparable to that on methionine-supplemented medium are reported as in Table 1.
b
The indicated tonB plasmids were introduced into the tonB strain RK5043 to evaluate their ability to complement the defect in CN-Cbl utilization. No btuB-carrying plasmid was present.
c
The indicated plasmids were introduced into btuB strain RK5016 in combination with compatible plasmid pAG1 derivatives carrying the wild-type btuB gene or the L8P- or V10P-encoding alleles, as indicated.