title: Differences in the incorporation of [3H]-glucosamine into nascent polypeptide chains on free polysomes and two fractions of membrane-bound polysomes in mouse myeloma cells.
abstract: The incorporation of [3H]-glucosamine into polypeptides of three fractions of polysomes in MPC-11 cells was studied. After short term incubation greatest incorporation was observed in a fraction of membrane-bound polysomes, which after nitrogen cavitation of cells, remained bound to the endoplasmic reticulum (ER) associated with the nucleus (fraction 2). Polypeptide chains on membrane-bound polysomes in the microsomal fraction (fraction 1) and free polysomes contained much less radioactivity. Since nascent polypeptide chains contained within membrane-bound polysomes of fraction 2 are glycosylated at an earlier stage than those in fraction 1 it is likely that this represents a difference in type of proteins synthesized in the respective fractions of ER.
mesh_terms: D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005944:Glucosamine / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D011132:Polyribosomes / Q000378:metabolism*
chemical_list: D010455:Peptides; D005944:Glucosamine