Title: Ribonuclease and trypsin treatment of ribosomes and polyribosomes from sea urchin eggs
Abstract: 1. Eggs of the sea urchin Lytechinus pictus were labeled, in vivo, with [3H]-uridine during oögenesis. RNA-labeled ribosomes and polyribosomes isolated from homogenates before and after fertilization were treated with ribonuclease, trypsin or trypsin followed by ribonuclease and then examined by sucrose density-gradient centrifugation. The trypsin was first freed of significant ribonuclease contamination by Sephadox chromatography. The experiments confirm that only a small portion of the ribosomal aggregates from homogenates of unfertilized eggs are ribonuclease sensitive and active in vivo in protein synthesis; that greater numbers of ribosomal aggregates are present in homogenates after fertilization; and that most of the aggregates from homogenates of fertilized eggs are ribonuclease sensitive and synthetically active. 2. Ribosomes from unfertilized and from fertilized eggs are alike in sedimentation velocity. Upon trypsin treatment the ribosomes, before or after fertilization, dissociate into two subunits. 3. Most of the ribonuclease-sensitive polyribosomes from fertilized eggs remain intact after trypsin treatment, even under conditions in which the single ribosomes undergo partial degradation. A maximum value of 40% was obtained for the dissociability by ribonuclease of the ribosomal aggregates from unfertilized eggs and this increased to 90% after trypsinization. The mechanism of the sensitization by trypsin and the nature of the changes upon fertilization are discussed. 4. The data suggest that ribonuclease-resistant polyribosomes may be one site of “nasked” messenger RNA in unfertilized eggs.
Publication Year: 1968
Publication Date: 1968-08-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 22
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