The 46 kDa mannose-6-phosphate receptor contains a signal for basolateral sorting within the 19 juxtamembrane cytosolic residues.

The cytosolic domain of the 46kDa mannose-6-phosphate receptor (MPR 46) contains a signal that mediates sorting of the receptor and of a reporter protein to the basolateral surface domain of Madin–Darby canine kidney cells. Progressive trunc- ation of the 67 cytosolic residues indicated that the 19 juxta- membrane residues are sufficient for basolateral sorting. Ala- nine glycine-scanning mutagenesis identified Glu-11 and Ala-17 as the critical residues between residues 7 and 19. Glu-11 is also of critical importance for the one of the three internalization signals in the cytosolic tail of the receptor [Denzer, Weber, Hille- Rehfeld, von Figura and Pohlmann (1997) Biochem. J. 326, 497–505]. Although overlapping, the signals for basolateral sorting and internalization depend on different residues. The basolateral sorting signal of MPR 46 is distinct from tyrosine- or dileucine-based basolateral sorting signals and also lacks simi- larity to the few other basolateral signals that do not fall into these two classes.