Selective silver-staining methods for RNA and proteins in the same polyacrylamide gels.

Two silver-staining methods for selective and ultrasensitive detection of RNAs and proteins in the same polyacrylamide gels were developed, both derived from procedures recommended for protein staining. The first, a double-staining technic with Coomassie brilliant blue and ammoniacal silver, allows visualization of RNAs as negative bands and proteins as dark brown bands. The second is also a double-staining technique, but uses silver in both steps. This second method develops the RNA bands first and then the protein bands. These techniques, especially the second, permit characterization of the different components of ribonucleoproteic complexes in the same electrophoresis gels.

Partial reassembly of active 60S ribosomal subunits from rat liver following treatment with dimethylmaleic anhydride.

Rat liver 60S ribosomal subunits were treated with dimethylmaleic anhydride, a reagent for protein amino groups, at a 1/15,000 mol/mol ratio. This caused the dissociation of specific proteins, which were separated from the 56S residual core particles by centrifugation and identified by two-dimensional gel electrophoresis. The core particles lacking 30% of the total proteins retained most of the initial activity measured by the puromycin reaction but only small percentages of activities measured by polyphenylalanine synthesis, elongation-factor-2(EF-2)-dependent GTP hydrolysis and EF-2-mediated GDP binding. Upon reconstitution, the complementary amount of split proteins was incorporated into ribosomal particles, which had almost the same catalytic activities and biophysical properties (density, sedimentation coefficient and capability to reassociate to 40S subunits) as the original subunits.

Modifications of 60 S ribosomal subunits induced by the ricin A chain.

Incubation of 60 S ribosomal subunits with the ricin A chain reduced their stability during heat treatment. The toxin shifted the thermal denaturation curve of the subunits towards lower temperatures, in a similar way to that produced by the decrease in Mg2+ concentration. A brief heating (3 min at 57 degrees C), which did not affect control subunit activity, enhanced protein synthesis inhibition of the toxin-treated subunits that released more 5 S RNA, in the form of nucleoprotein complex(es) with protein L5 and phosphoproteins P1P2 (RNPH), than did heated control subunits [(1984) Eur. J. Biochem. 143, 303-307]. No nuclease activity tested on 60 S subunits and purified 5 S and 5.8 S RNA was found associated with the toxin. The results suggest that the toxin induced a limited conformational change of the 60 S subunit, which destabilized the interaction between RNPH and the rest of the subunit.

Photo-induced protein cross-linking to 5S RNA and 28-5.8S RNA within rat-liver 60S ribosomal subunits.

Rat liver 60S ribosomal subunits were irradiated with 254-nm ultraviolet light (1.26 X 10(4) quanta/subunit), under conditions which preserved their functional activity. Cross-linked RNA-protein complexes were recovered after unreacted proteins had been removed by repeated acetic acid extractions. Proteins linked to the whole rRNA, to 5S RNA and to 28-5.8 S RNAs were identified by two-dimensional gel electrophoresis after RNA hydrolysis by ribonucleases T1 and A. Our results showed that numerous proteins interact with rRNAs (at least ten with 28-5.8 S RNA, eight with 5S RNA and among these three are common to both) and have been discussed in the light of all the available data.