Table 2.
Translocation of UDP-glucose into an ER- and Golgi-enriched vesicle fractiona
| Substrate | Temp (°C) | [Sm] (μM) | Solute (pmol/mg protein)
|
[Si] (μM) | [Si]/[Sm] | ||
|---|---|---|---|---|---|---|---|
| St | So | Si | |||||
| UDP-Glc | 30 | 2 | 55.4 | 2.9 | 52.5 | 43.7 | 21.9 |
| UDP-Glc | 0 | 2 | 6.1 | 2.9 | 3.2 | 2.7 | 1.35 |
| UDP-Glcb | 30 | 2 | 2.3 | 2.9 | 0 | 0 | 0 |
| UDP-GlcNAc | 30 | 2 | 3.2 | 2.9 | 0.3 | 0.2 | 0.1 |
| UDP-Gal | 30 | 2 | 12.4 | 2.9 | 9.5 | 7.9 | 3.9 |
| GDP-Man | 30 | 2 | 39.7 | 2.9 | 36.8 | 30.7 | 15.3 |
| Glucose | 30 | 4 | 10.7 | 5.8 | 4.9 | 4.1 | 1 |
a
Radioactive substrates (3000 cpm/pmol) were incubated for 3 min at the indicated temperatures with P2 vesicle fraction (1.5 mg of protein) in 1 ml of buffer B. Translocation was determined by a centrifugation assay as described in detail (34). Sm and [Si] are, respectively, solutes in the medium and within vesicles. St, So, and Si are respectively, total solute and solute outside and inside vesicles. Calculations are described in Materials and Methods. Results are average of triplicate determinations.
b
Triton X-100, 0.05%, was added to the assay.