Table 2. Reductase activity of hPDI and its mutants.

Protein	Relative activity (%)	Inter-domaininteraction
WT	100
R97E	68.2 ± 5.7***	a and b'
D180R/D181R	26.7 ± 4.5***	a and b
K326E	56.0 ± 5.6***	b' and a'
E431K	53.6 ± 4.8***	b' and a'
K326E/E431K	82.2 ± 7.4*	b' and a'
P235G	61.3 ± 2.6***	b and b'

The mutants were designed to interfere with inter-domain interactions. The activity was determined according to insulin reduction as described in the text. The activity of WT PDI was taken as 100%. Date were expressed as mean ± S.D. (n = 3). Statistical significance was analyzed by using two-tailed t-test, ^*** and ^* represent P<0.001 and P<0.05, respectively.