Overexpression of Nyv1p suppresses the ALP trafficking defect of the ykt6-13 mutant. ykt6-13 (YKY11) cells carrying an empty plasmid or a multicopy plasmid with either YKT6, NYV1, or SFT1 were labeled for 10 min at 30°C and chased for the indicated times. Cell extracts were subjected to immunoprecipitation with antibodies to ALP (A), CPY (B), or API (C), and the samples resolved by SDS-PAGE and visualized by autoradiography. I, intracellular; E, extracellular; *, ALP degradation product.