Fig. 6. Recycling between endosomes and the plasma membrane depends on the amino-acid composition of the tyrosine motif. LAP reporter proteins that contain either the LAP7 tail or the Lamp 1 tail, but both with variations in the position +2 and +3 of the tyrosine motif (LAP7/TI and Lamp 1/HV, Fig. 4), were expressed and assayed for recycling between endosomes and the plasma membrane exactly as described under Fig. 3. Changing the residues +2 and +3 within the LAP tyrosine motif to the respective residues of Lamp 1 (LAP7/TI) abolished recycling to a high extend, whereas changing the residues +2 and +3 within the Lamp-1 tyrosine motif to the respective LAP residues induces efficient recycling (Fig. 3; Table 2). Owing to the gel system used here, the mature form of LAP is visible in the total cell extracts (indicated by the asterisk).