TABLE 2.
The effect of urea and calcium on surface pressure changes caused by IpaC
| Urea presentb | Ca2+ addedc | Change in lipid pressure upon addition of IpaC (ΔΠ)a at an initial lipid pressure (dynes/cm) of:
|
Multiple of increase in lipid pressure at 15 dynes/cm versus initial lipid pressure at 3 dynes/cm | |||
|---|---|---|---|---|---|---|
| 3 | 5 | 10 | 15 | |||
| − | − | 0.3 | 1.0 | 1.4 | 2.1 | 7.0 |
| − | + | 0.6 | 1.0 | 1.7 | 2.1 | 3.5 |
| + | − | 1.1 | 1.3 | 2.4 | 2.9 | 2.6 |
| + | + | 2.2 | 2.8 | 3.4 | 4.1 | 1.9 |
a
The data shown are representative results from a series of at least three independent experiments that generated similar results (deviation, ≤10%).
b
Samples were prepared in 2 M urea as described in the text and rapidly diluted into 0.1 M Tris (pH 7.4) to promote protein refolding. The final concentration of urea was less than 50 mM following addition to the aqueous subphase in all cases.
c
CaCl2 was added to a final concentration of 10 mM.