title: Synthesis of exported proteins by membrane-bound polysomes from Escherichia coli.
abstract: A membrane-bound fraction of polysomes of Escherichia coli has been isolated after lysis of cells without the use of lysozyme. Protein-synthesis studies in vitro show that membrane-bound and free polysomes are different in the following respects. 1. Membrane-bound polysomes synthesize proteins which are exported from the cell. The products include proteins of the outer membrane and a secreted periplasmic protein, the maltose-binding protein. 2. The major product synthesized by free polysomes is elongation factor Tu, a soluble cytoplasmic protein. 3. The activity of membrane-bound polysomes in vitro is more resistant to puromycin than is the activity of free polysomes. In addition, the mRNA associated with membrane-bound polysomes is more stable than the bulk of cellular mRNA as revealed by studies with rifampicin.
mesh_terms: D001665:Binding Sites; D002462:Cell Membrane / Q000502:physiology / Q000648:ultrastructure; D004926:Escherichia coli / Q000378:metabolism* / Q000648:ultrastructure; D005779:Immunodiffusion; D007700:Kinetics; D008854:Microscopy, Electron; D008970:Molecular Weight; D009113:Muramidase; D010445:Peptide Elongation Factors; D011132:Polyribosomes / Q000378:metabolism* / Q000648:ultrastructure; D011233:Precipitin Tests; D014176:Protein Biosynthesis / Q000187:drug effects; D011691:Puromycin / Q000494:pharmacology; D012269:Ribosomal Proteins / Q000096:biosynthesis*
chemical_list: D010445:Peptide Elongation Factors; D012269:Ribosomal Proteins; D011691:Puromycin; D009113:Muramidase