Phosphorylation of the cytoplasmic tail of the 300-kDa mannose 6-phosphate receptor is required for the interaction with a cytosolic protein.
The cytoplasmic tail of the human 300-kDa mannose 6-phosphate receptor (MPR 300-CT) is an excellent substrate for casein kinase II in vitro. The phosphorylated MPR 300-CT was cross-linked by means of bis(sulfosuccinimidyl)suberate mainly to a cytosolic protein of 35 kDa (referred to as TIP 35) and to 35- and 91-kDa proteins salt-washed from bovine brain membranes. Gel filtration suggested that TIP 35 is part of a higher molecular mass complex of approximately 130-150 kDa. Inhibition studies, using non-phosphorylated and phosphorylated MPR 300-CT and cross-linking, indicate that the interaction with TIP 35 is phosphorylation-specific. Furthermore, TIP 35 was only cross-linked to the MPR 300-CT phosphorylated by casein kinase II whereas the MPR 300-CT phosphorylated by protein kinase A failed to cross-link to TIP 35. These results indicate that the cytoplasmic tail of the MPR 300 interacts with a cytosolic protein depending on the phosphorylation by a casein kinase II-like kinase. The cross-linking with salt-washed membrane proteins, however, is inhibited by non-phosphorylated MPR 300-CT, suggesting that different structural determinants in the MPR 300-CT interact with cytosol- and membrane-derived proteins.
Rosorius
O
O
Institute for Biochemistry II, University of Göttingen, Federal Republic of Germany.
Issinger
O G
OG
Braulke
T
T
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002478:Cells, Cultured; D003432:Cross-Linking Reagents; D003593:Cytoplasm / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism*; D017527:Receptor, IGF Type 2 / Q000378:metabolism*; D013388:Succinimides
D003432:Cross-Linking Reagents; D011506:Proteins; D017527:Receptor, IGF Type 2; D013388:Succinimides; C035760:bis(sulfosuccinimidyl)suberate