Informational ribonucleoprotein particles of newt oocytes: polyribosome-associated ribonucleoproteins.
Various species of rapidly labelled, informational ribonucleoproteins can be isolated from homogenates of newt oocytes. Polyribosome-associated ribonucleoprotein can be separated from heterogeneous nuclear ribonucleoprotein and free cytoplasmic ribonucleoprotein by sucrose gradient centrifugation. The polyribosome-associated ribonucleoprotein can be released from the ribosome complex by treatment with low concentrations of EDTA and has the following properties: 1. It is rapidly labelled with [3H]uridine under condition (incubation of oocytes for 4 h and less at 20 degrees C) where there is no detectable labelling of ribosomal subunits. 2. It is heterogeneous in size, consisting of particles most of which sediment between 40 S and 80 S. 3. Its sedimentation coefficient is related directly to the size of the polyribosomal complex from which it is derived. 4. Its density ranges from 1.35 g/cm3 to 1.55 g/cm3 irrespective of size. This indicates protein to RNA ratios of 4:1 to 2:1. 5. It is active, when complexed with ribosomes, in cell-free protein synthesis. It is concluded that this polyribosome-associated ribonucleoprotein is functional messenger and its role in oocyte maturation is discussed.
Sommerville
J
J
Department of Zoology, The University, St. Andrews, Fife, Great Britain.
D000818:Animals; D002250:Carbon Radioisotopes; D002474:Cell-Free System; D002499:Centrifugation, Density Gradient; D004492:Edetic Acid / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism*; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D012261:Ribonucleoproteins / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000235:genetics; D012455:Salamandridae / Q000378:metabolism*; D014316:Tritium
D002250:Carbon Radioisotopes; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear; C026452:messenger ribonucleoprotein; D014316:Tritium; D004492:Edetic Acid