Ribosomal Proteins

Abstract

50 S ribosomal subunits of Escherichia coli obtained by zonal centrifugation in B XV rotors were treated with various concentrations of LiCl in the absence and presence of urea. This treatment resulted in three protein fractions, each of which was subjected to CM-cellulose chromatography. Gel filtration in Sephadex G-100 (and preparative polyacrylamide electrophoresis) were used for further separation. The purity of the isolated proteins was better than 950/, as shown by four methods. Proteins were isolated in yields of 6-90 mg depending mainly on the number and kind of purification steps.Instead of fractionation with LiCl prior to column chromatography, precipitation of extracted proteins at various concentrations of ammonium sulfate was tested. This method is useful if a given protein, e.g. from mutants is wanted in large quantity.The protein moiety of ribosomes is very complex [I]. 30 S ribosomal subunits of Escherichia coli contain 21 proteins which were isolated and studied in various laboratories [ 2 -141. The number of ribosomal proteins in E . coli 50s subunits is about 50°/, higher than in 30 S subunits [8,10,15]. Because of the large number of 50 S proteins and their relatively similar chemical and physical properties, separation and isolation are very difficult and only possible by a combination of various methods which separate according to different criteria, e.g. protein charge and size as well as interaction of ribosomal proteins with each other and/or with ribosomal RNA in the particle.The present paper describes the isolation of 50s proteins in relatively large quantities (6-90 mg). The chemical, physical and immunological properties of the ribosomal proteins isolated by these methods are described elsewhere [I1 -14,271. MATERIAL AND METHODSIsolation of ribosomes and subunits from E . coli K12 (strain A19) and separation of proteins by CMcellulose and Sephadex G-I00 were described earlier [16]. Treatment of 50s subunits with LiCl followed previous procedures [17-221 with the following modifications.12g of 50s subunits were brought with 0.05M Tris-HC1 pH 7.8, 0.01 M Mg2+ to a concenbration of 10 mg/ml and dialyzed a t 4 "C for 4 h against 2 x 5 1 of 0.05 Tris-HC1 pH 7.8, 0.01 M Mg2+ and then for I2 h against 3 x 5 1 of the same buffer with 0.1 M Mg2+.One volume (= 1200ml) of 50s and one volume of cold 4 M LiC1, 0.1 M magnesium acetate, were mixed and stirred for 8 h in ice water. After centrifugation for 16 h a t 25000 rev./min in Spinco 42 rotors the supernatant (= UI) was dialyzed for 18 h against 4 x 5 1 100/, acetic acid plus 0.1 O/, mercaptoethanol.The sediment was resuspended in 1200 ml of cold 0.01 M Tris-HC1 pH 7.8, 0.1 M Mg2+, and dialyzed a t 4 "C for 4 h against 5 1 of this buffer and then for I2 h against 3 x 5 1 0.05 M Tris pH 7.8, 0.1 M Mg2+. The suspension was diluted 1 : 1 with cold 7 M LiC1, 0.1 M Mg2+, stirred in ice water for 8 h and centrifuged as described. The supernatant (= UII) was dialyzed as described for UI.The sediment was resuspended in 600ml cold distilled water. The...

Identification of 50S Proteins at the Peptidyl-tRNA Binding Site of Escherichia coli Ribosomes

“…The proteins of the 50S particle are in general less reactive towards added enzymes or organic reagents than those of the 30S particle (8-10; 12; Litman, D. & Cantor, C. R., in preparation). One of the most reactive 50S proteins toward fluorescene-isothiocyanate (9) and trypsin digestion (8) (12)(13)(14). Fahnestock et al (15) have shown that although L3 from B. stearothermophilus is not required for in vitro binding of other proteins in reconstitution of the 50S particle, it is necessary for assembly of active 50S subunits.…”

The primary structure of protein L27 from the peptidyl‐tRNA binding site of Escherichia coli ribosomes

“…Protein L27 was prepared as previously described [5] and was provided by Dr H. G. Wittmann, TPCKtrypsin and TLCK-chymotrypsin were purchased from Merck (Darmstadt), Staphylococcus protease from Miles (Slough, UK), thermolysin from Serva (Heidelberg), citraconic anhydride from Pierce (Rotterdam), cellulose thin-layer plates, Polygram cel 300, from Machery and Nagel (Diiren) and micro polyamide plates F 1700 from Schleicher and Schtill (Dassel).…”

A ribonuclease-resistant region of 5S RNA and its relation to the RNA binding sites of proteins L18 and L25

“…Ribosomal proteins L18 and L25 were prepared either by the method of Hindennach et al (17), or that of Chen-Schmeisser and Garrett (18) with a final fractionation of the proteins on a phosphocellulose column (6). L25 was also prepared by treating ribosomes at pH 3.8 as described by Brosius (19).…”