Phosphorylation of GDI and membrane cycling of rab proteins.
Membrane transport is known to be regulated by protein phosphorylation and by small GTPases of the rab family. Using specific antibodies, we have identified a 55 kDa phosphorylated protein which co-immunoprecipitated with the cytosolic forms of rab5 and other rab proteins. We demonstrate, on the basis of its mobility in two-dimensional electrophoresis gels and its immunological properties, that this protein is rab GDI (p55/GDI). We also found that, a minor fraction of p55/GDI is membrane associated, but, whilst also complexed with rab proteins, it is not phosphorylated. On the basis of these data we suggest that the cycling of rab proteins between membranes and cytosol is regulated by phosphorylation of p55/GDI.
Steele-Mortimer
O
O
Cell Biology Programme, European Molecular Biology Laboratory, Heidelberg, Germany.
Gruenberg
J
J
Clague
M J
MJ
D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007525:Isoelectric Focusing; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism*; D011233:Precipitin Tests; D020696:rab5 GTP-Binding Proteins
D008565:Membrane Proteins; D010750:Phosphoproteins; D019204:GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins