The Duck‐Globin Messenger‐Ribonucleoprotein Complex

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Abstract
The duck globin messenger ribonucleoprotein complex which contains the biologically active globin mRNA and two major protein components associated with it, has been further characterized.When analysed on gradients of increasing ionic strength, the mRNA · protein particle showed resistance to 0.25 M LiCl, a condition which fully dissociates artificial RNA · protein complexes, and was partially resistant to 0.75 M LiCl.By polyacrylamide gel electrophoresis the particle was shown to consist of one major component A and two minor components B and C of increasing mobility. Component A and C were ribonucleoproteins, B consisted of free proteins; no free RNA could be detected.Component A, when analysed on dodecylsulfate gels contained all the proteins of the complex: the two major bands of molecular weight 49000 and 73000, diffuse minor bands in the 52000 to 64000 molecular weight range and three more sharp bands in the 86000 to 120000 range. Components B and C contained only some of the protein bands. It is concluded that the composition of the mRNA protein particle is more complex than was originally thought.The protein bands with molecular weights of 73000, 64000 and 49000 were found to be phosphorylated, containing phosphoserine.Using the method of dark‐field electron miroscopy, we were able to resolve for the first time internal structural details of the mRNA · protein complex and of the mRNA. The proteins seem to be attached all along the mRNA chain in 4 to 7 distinct blobs, probably in regions of high secondary mRNA structure.Taken together, these results strongly suggest that mRNA · protein particles are not artefacts formed during cell lysis and probably have a biological significance.