The membrane of the rough endoplasmic reticulum contains cytoplasmically exposed high affinity GTP-binding sites.
Binding experiments using [14C]GTP and rat liver rough microsomes gave Scatchard plots with Kd congruent to 0.1 microM and a binding capacity congruent to 40 pmol/mg microsomal protein. Removal of the ribosomes did not modify the binding parameters. GTP was competed out by GTP analogues but not by ATP. Limited proteolysis of rough microsomes decreased the GTP-binding capacity and prevented GTP from suppressing the latency of mannose-6-phosphatase and of the synthesis of dolichol-linked chitobiose. The GTP-binding protein is probably involved in these effects of GTP. Its function could be to act in the association-dissociation of membrane components at the ribosome-membrane junction.
D000818:Animals; D002458:Cell Fractionation; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats
D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins