Figure 3.

Characterization of Golgi-enriched membrane fractions. Aliquots of 10 μg protein from the Golgi-enriched membrane fractions derived from either normal (+/+) or the MPR-negative (−/−) cells were boiled in 1× SDS-sample buffer, resolved on polyacrylamide gels, and then transferred to nitrocellulose filters. The blots were probed with anti-mouse LAMP-1 antibody, mAb 1D4B, polyclonal anti–α-mannosidase II antiserum, or the anti–AP-1 ς1 subunit antibody, DE/1. Only the relevant portion of each blot is shown. Galactosyltransferase activity in 10-μg protein aliquots from the normal (+/+) or MPR-negative (−/−) Golgi-enriched fractions was determined. At this protein concentration, the enzyme activity is within the linear range of this assay.