Topological orientation of mitochondrial GDPmannose: dolichyl-monophosphate mannosyltransferase in the outer membrane.
Previous studies have shown the existence of an autonomous mitochondrial GDPmannose:dolichylmonophosphate mannosyltransferase, located in mitochondrial outer membrane of liver cells. As nothing is known about glycosylation sites in mitochondria, we have investigated the topological orientation of this enzyme in intact mitochondria, using controlled proteolysis with trypsin. Mitochondria were purified sequentially by mild ultrasonic treatment and sucrose density gradient. Purity and homogeneity of mitochondrial fraction were assessed by electron microscopy and specific marker enzymes measures. Our data provide evidence for a mitochondrial GDPmannose:dolichylmonophosphate mannosyltransferase facing the cytoplasmic side of the outer membrane. However, the exposure of this enzyme to the water phase has been shown to be dependent on the ionic strength of the environment.
Gasnier
F
F
University of Lyon, Department of Biochemistry, Oullins, France.
Louisot
P
P
Gateau-Roesch
O
O
D000818:Animals; D002458:Cell Fractionation; D002499:Centrifugation, Density Gradient; D004789:Enzyme Activation / Q000187:drug effects; D006155:Guanosine Diphosphate Mannose / Q000032:analysis*; D006602:Hexosyltransferases / Q000032:analysis*; D007425:Intracellular Membranes / Q000201:enzymology* / Q000648:ultrastructure; D008364:Mannosyltransferases / Q000032:analysis* / Q000378:metabolism; D051379:Mice; D008815:Mice, Inbred Strains; D008930:Mitochondria, Liver / Q000201:enzymology* / Q000648:ultrastructure; D009702:Nucleoside Diphosphate Sugars / Q000032:analysis*; D009994:Osmolar Concentration; D014357:Trypsin / Q000494:pharmacology
D009702:Nucleoside Diphosphate Sugars; D006155:Guanosine Diphosphate Mannose; D006602:Hexosyltransferases; D008364:Mannosyltransferases; D014357:Trypsin