Figure 2.

Phosphorylation of Lysosomal Enzymes by S1-S3

GNPTAB^−/− HeLa cells were co-transfected with either WT or S1-S3 α/β precursor cDNAs, along with expression plasmids for four lysosomal enzymes. Forty-eight hours post-transfection, cells were labeled for 2 hr with [2-³H]-mannose, followed by immunoprecipitation of the proteins secreted into the media and determination of the percentage N-glycans containing one (1PM) or two (2PM) Man-6-P residues. The absolute values of the percentage glycans phosphorylated are shown. *p < 0.05, **p < 0.01. Error bars represent mean ± SD.