lvsB-null cells process and target lysosomal α-mannosidase normally but oversecrete the mature enzyme. Wild-type control, lvsA-null, and lvsB-null cells were pulsed with [35S]methionine, washed, and chased in fresh HL-5. At each time point during the chase period, α-mannosidase was immunoprecipitated from both the medium, to detect secreted α-mannosidase, and cell lysates, to detect intracellular α-mannosidase. Immunoprecipitates were subjected to SDS-PAGE, followed by fluorography.