TABLE 2.
Sensitivity of spontaneous TonB mutants to colicins D and B and variants mutated at their TonB box
| Colicin mutant | TonB boxa | Sensitivityc to:
|
||
|---|---|---|---|---|
| WT | D1 (R158S) | K19 (P161L) | ||
| WT ColD | GHSMVVWPSTG | 4 | R | R |
| H17D | D | 4 | R | R |
| S18T | T | 4 | 2-3 | 2 |
| S18A | A | 4 | R | R |
| S18L | L | 4 | R | R |
| S18I | I | 4 | R | R |
| S18C | C | 4 | R | R |
| S18R | R | 4 | R | R |
| M19I | I | 4 | R | 3-4 |
| M19V | V | 4 | R | 2-3 |
| M19L | L | 4 | R | 2 |
| M19P | P | R | R | R |
| M19C | C | 2 | R | R |
| V20E | E | 4 | R | R |
| V21E | E | R | R | R |
| W22E | E | R | R | R |
| ColBb | DT | 4 | [0-1] | [0-1] |
| FepAb | DTI | 4 | R | 3-4 |
| FhuAb | DTIT | 4 | R | R |
| BtuBb | DTL | 4 | R | 2 |
| Cirb | ET | 4 | R | R |
| ColMb | ETLT | 3 | R | R |
| ColIab | EI A | 2-3 | R | R |
| WT ColB | GDTMVVWPSTG | 4 | 3-4 | 3-4 |
| D17H | H | 4 | 3-4 | 3-4 |
| T18S | S | 4 | 2 | 2 |
| T18R | R | 4 | 3-4 | 3-4 |
| ColDb | HS | 4 | 3 | 2-3 |
| FepAb | I | 3-4 | 3 | 3-4 |
| Cirb | E | 3-4 | 2 | 2 |
Positions of the site-directed mutation(s) introduced in the colicin (D or B) TonB box (underlined) are shown. The leftmost position in the sequence is position 16.
Changes necessary to introduce different wild-type TonB box motifs are given.
The cytotoxicity of the wild-type (WT) or mutant colicins D and B was tested with wild-type and TonB mutant strains as described for Table 1. Values indicate the last serial 10-fold colicin dilution that resulted in a clear zone of growth inhibition. R indicates resistance to undiluted colicin preparation (numbered as 0). Values in brackets indicate the dilution corresponding to the turbid zone of marginal growth inhibition. Functionally important substitutions are indicated in bold.