Small GTP-binding proteins on rat liver lysosomal membranes.
GTP-binding proteins have been identified on the membranes of highly purified dextran-filled lysosomes (dextranosomes) and Triton-filled lysosomes (tritosomes) obtained from rat liver. Autoradiography of blots of lysosomal membrane proteins incubated with [alpha-32P]GTP revealed the presence of several specific GTP-binding proteins with a relative molecular mass (M(r)) predominantly in the range of 26-30 kDa. These GTP-binding proteins migrated slower in polyacrylamide gels than purified c-Ha-ras protein expressed in E. coli, whose apparent M(r) was 23 kDa in the same blot. The relative contents of GTP-binding proteins in lysosomal membranes were comparable or greater than that of plasma membranes and of microsomes. Chemical extraction showed that lysosomal GTP-binding proteins were more tightly associated with the membranes than with microsomal GTP-binding proteins. The possible involvement of lysosomal GTP-binding proteins in cellular functions including vacuolar (lysosomal) acidification and organellar dynamics are discussed.
Sai
Y
Y
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Kanazawa University, Japan.
Ohkuma
S
S
D000818:Animals; D002499:Centrifugation, Density Gradient; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism*; D008970:Molecular Weight; D051381:Rats
D019204:GTP-Binding Proteins