Endoplasmin is a reticuloplasmin.
The location of endoplasmin in the endoplasmic reticulum was investigated by biochemical and immunoelectron microscopic analyses. The protein could be obtained in a soluble form by procedures that do not involve the use of any detergents. The soluble protein has the amino- and carboxy-terminal sequences of the intact molecule, showing that it has not been proteolysed. Application of the Triton X-114 phase-separation test does not reveal significant hydrophobicity in the molecule. Immunogold labelling studies on cells with a dilated endoplasmic reticulum (ER) lumen show that endoplasmin is uniformly distributed throughout the lumen, with no evidence of a preferential association with the membrane. These studies clearly demonstrate that endoplasmin is a luminal protein of the ER, i.e. a reticuloplasmin, and not an integral membrane protein.
Koch
G L
GL
Medical Research Council Laboratory of Molecular Biology, Cambridge, England.
Macer
D R
DR
Wooding
F B
FB
D000818:Animals; D004721:Endoplasmic Reticulum / Q000032:analysis* / Q000648:ultrastructure; D007150:Immunohistochemistry; D008562:Membrane Glycoproteins / Q000032:analysis*; D051379:Mice; D008854:Microscopy, Electron; D008861:Microsomes / Q000378:metabolism; D012995:Solubility
D008562:Membrane Glycoproteins; C053387:endoplasmin