TABLE 2.
Soluble and insoluble glucan-synthesizing activities of Gtfs
| Gtf | Without dextran T10
|
With dextran T10
|
Stimulation by dextranb
|
|||||
|---|---|---|---|---|---|---|---|---|
| Glucan-synthesizing activitya (mU/mg of protein)
|
SG/IG ratio | Glucan-synthesizing activity (mU/mg of protein)
|
SG/IG ratio | |||||
| SG | IG | SG | IG | SG | IG | |||
| GtfB | 0.33 | 2.98 | 0.11 | 0.67 | 3.60 | 0.19 | 2.01 | 1.21 |
| GtfC | 0.26 | 1.81 | 0.14 | 0.69 | 2.44 | 0.28 | 2.69 | 1.35 |
| GtfB-ms2 | 0.03 | 1.98* (−34) | 0.02 | 0.33 | 2.36* (−34) | 0.14 | 10.53# | 1.19 |
| GtfB-ms3 | 0.29 | 0.59* (−80) | 0.50 | 0.39 | 1.06* (−71) | 0.37 | 1.34 | 1.79 |
| GtfB-D411N | 0.16 | 0.56* (−81) | 0.28 | 0.17 | 0.65* (−82) | 0.27 | 1.09 | 1.16 |
| GtfB-D413N | 0.08 | 0.64* (−78) | 0.13 | 0.10 | 0.63* (−83) | 0.16 | 1.22 | 0.97 |
| GtfB-V412I | 0.01 | 3.33* (+12) | 0.003 | 0.56 | 3.97* (+10) | 0.14 | 59.12# | 1.19 |
| GtfC-V438I | 0.02 | 2.17* (+19) | 0.01 | 0.40 | 2.66* (+8.8) | 0.15 | 22.63# | 1.12 |
| GtfB-E422Q | 0.08 | 0.64* (−62) | 0.13 | 0.24 | 1.45* (−59) | 0.17 | 3.06 | 1.08 |
| GtfC-E448Q | 0.24 | 0.58* (−68) | 0.41 | 0.42 | 1.03* (−58) | 0.40 | 1.73 | 1.76 |
| GtfB-D411/413N | 0 | 0 | 0 | 0 | ||||
a
Expressed as specific activity for SG and as IG synthesized from [U-14C]sucrose. Values in parentheses represent percentages of reduction or increase of IG synthesized by the mutants, calculated as 100-% IG for the original GtfB or GtfC, which was normalized to 100%. Average values from quadruplicate assays are given, and the standard deviation of individual set of assays is within 12% of the average value. ∗, significant difference between mutant and wild-type proteins (P < 0.01 by Student’s t test; t = 3.707).
b
Expressed as the ratio of SG or IG in the presence and absence of dextran T10. #, significant increase in soluble glucan synthesis stimulated by dextran (P < 0.001).