TABLE 3.
Properties of trbB mutants
| trbB mutant | Transfer frequencya | Activity ofb:
|
Assembly to hexameric rings | Trans- dominancec | ||||
|---|---|---|---|---|---|---|---|---|
| dATPase (pH 9.5) | GTPase
|
ATPase
|
||||||
| pH 7.5 | pH 9.5 | pH 7.5 | pH 9.5 | |||||
| wt | 2.0 × 100 | 4.48 ± 0.5 | 0.9 ± 0.1 | 1.88 ± 0.3 | 0.55 ± 0.1 | 0.91 ± 0.1 | + | 4.2 × 10−1 |
| wtd | 2.27 ± 0.4 | 0.26 ± 0.03 | 0.34 ± 0.03 | 0.28 ± 0.03 | 0.31 ± 0.03 | + | ||
| K161A | <10−7 | <0.03 | <0.03 | <0.03 | <0.03 | <0.03 | + | 1.4 × 10−4 |
| D186A | 4.8 × 10−1 | <0.03 | 0.11 ± 0.03 | <0.07 | <0.07 | 0.22 ± 0.03 | + | NDe |
| R217T | 9.6 × 10−1 | <0.07 | <0.09 | <0.03 | <0.03 | <0.03 | + | ND |
a
Transfer frequencies are expressed as transconjugants per donor cell.
b
The NTPase activities were analyzed with a 1.5 μM concentration of the respective protein at 30°C for 20 min. Activity values are given in micromoles of released NDP per minute.
c
For determination of trans-dominance of trbB mutants, merodiploid strains HB101(pSK126 trbBwt, pDB179 trbBmut) expressing both wt and mutant trbB genes were employed as donor strains. Transfer frequencies are expressed as transconjugants per donor cell.
d
Purified using a 6 M urea extract as starting material.
e
ND, not determined.