Figure 8
MUC5B–GST interaction: a known concentration of GST was used to spike the purified MUC5B preparation. Then, the complex was isolated using a cesium chloride (CsCl) density gradient to detect the proportion of bound GST. A typical density-gradient profile (a) shows that all of the MUC5B mucin is recovered in the high-density regions (fractions 7–11), whereas approximately 15–20% of the GST was detected in the mucin region. CsCl density gradient with only GST (broken blue line) or MUC5B (broken magenta line) was used as controls. Four independent experiments using different preparations were summarized in (b) indicated that a significant amount of GST was present in the mucin fractions compared with the control (*P=0.002, **P=0.0005). (c) the GST activity measurements over the gradient of different concentrations of GST (GST100 μg, GST20 μg) including a similar concentration in the mucin fraction at 7A (∼15–20 μg) indicated that the GST activity peaks in approximately the first 3–4 fractions, but no measurable GST enzymatic activity was detected in the mucin-rich fractions (c). MUC5B preparation with no GST addition was used as a control. GST, glutathione S-transferase.
