title: Identification of a precursor pool of ribosome protein in Escherichia coli.
abstract: Antibodies prepared against proteins from 50S ribosomes of Escherichia coli also reacted with the supernatant proteins of a cell-free extract of E. coli which was ribosome-free. A reaction of immunological identity (Ouchterlony tests) was demonstrated for one of these supernatant proteins and one protein found in 50S ribosomes. Isotope experiments involving a shift from (14)C-leucine medium to (12)C-leucine medium showed that these proteins are not formed by breakdown of ribosomes during the preparation of cell-free extracts, but instead represent a pool of ribosome protein which is utilized during growth. In shift experiments from (14)C-leucine to (12)C-leucine medium, the kinetics of disappearance of labeled supernatant ribosome proteins (as measured by reaction with antibody) indicated that half the pool is depleted in 0.1 generation time at 37 C in glucose-salts medium. The pool was also depleted under conditions of amino acid starvation of a "relaxed" strain which accumulated "relaxed" particles. Most, if not all, of the protein present in "relaxed" particles was derived from the pool. The pool represented about 3 to 4% of the total soluble proteins in the ribosome-free supernatant fluid of an E. coli extract.
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis* / Q000378:metabolism; D002247:Carbon Isotopes; D002474:Cell-Free System; D002499:Centrifugation, Density Gradient; D004926:Escherichia coli / Q000032:analysis / Q000378:metabolism*; D007120:Immunochemistry; D005779:Immunodiffusion; D007930:Leucine / Q000378:metabolism; D011233:Precipitin Tests; D012270:Ribosomes
chemical_list: D001426:Bacterial Proteins; D002247:Carbon Isotopes; D007930:Leucine