The gene for the S7 ribosomal protein of Chlamydia trachomatis: characterization within the chlamydial str operon

The prokaryotic ribosomal operon, str, contains open reading frames for the two elongation factors, elongation factor G (EF-G) and elongation factor Tu (EF-Tu), and ribosomal proteins S7 and S12. The DNA sequence and predicted amino acid sequence for S7 from Chlamydia trachomatis are presented and compared with homologues from other prokaryotes. Also, the relationship of the S7 gene to the open reading frames for ribosomal protein S12 and EF-G is described. Significant amino acid homology is also noted when the amino-terminal sequence of chlamydial EF-G is compared with the cytoplasmic tetracycline resistance factors, tetM and tetO, from streptococci and Campylobacter jejuni. Related findings and possible resistance mechanisms for the newly recognized tetracycline-resistant clinical isolates of C. trachomatis are discussed.

An inhibitor of elongation factor G (EF-G) GTPase present in the ribosome wash of Escherichia coli: a complex of initiation factors IF1 and IF3?

An inhibitor of elongation factor G (EF-G) GTPase isolated from the ribosome wash of Escherichia coli was shown to stimulate the poly(A,U,G)- and initiation factor 2 (IF2)-dependent binding of N-formyl-[35S]Met-tRNAfMet to ribosomes. In the presence of saturating amounts of the EF-G GTPase inhibitor, neither addition of initiation factor 1 (IF1) nor addition of initiation factor 3 (IF3) caused a further stimulation of the formation of N-formyl-[35S]Met-tRNAfMET/poly(A,U,G)/ribosome complexes. Both IF1 and IF3 were shown to inhibit ribosome-dependent EF-G GTPase, especially when both initiation factors were added either in absence or in the presence of initiation factor 2 (IF2), poly(A,U,G) and N-formyl-Met-tRNAfMet. Therefore, we conclude that the EF-G GTPase inhibitor consisting of two polypeptide subunits with apparent molecular masses of 23,000 and 10,000 Da is a complex of initiation factors IF1 and IF3. The inhibition of EF-G GTPAse by IF3, but not the effects of IF1 in the presence or absence of IF3 could be reversed by increasing the Mg(2+)-concentration as already shown for the EF-G GTPase inhibitor. Therefore, IF1 as well as the EF-G GTPase inhibitor do not influence the ribosome-dependent EF-G GTPase by affecting the association of ribosomal subunits.

Phylogenetic depth of Thermotoga maritima inferred from analysis of the fus gene: amino acid sequence of elongation factor G and organization of the Thermotoga str operon

The gene (fus) coding for elongation factor G (EF-G) of the extremely thermophilic eubacterium Thermotoga maritima was identified and sequenced. The EF-G coding sequence (2046 bp) was found to lie in an operon-like structure between the ribosomal protein S7 gene (rpsG) and the elongation factor Tu (EF-Tu) gene (tuf). The rpsG, fus, and tuf genes follow each other immediately in that order, which corresponds to the order of the homologous genes in the str operon of Escherichia coli. The derived amino acid sequence of the EF-G protein (682 residues) was aligned with the homologous sequences of other eubacteria, eukaryotes (hamster), and archaebacteria (Methanococcus vannielii). Unrooted phylogenetic dendrograms, obtained both from the amino acid and the nucleotide sequence alignments, using a variety of methods, lend further support to the notion that the (present) root of the (eu)bacterial tree lies between Thermotoga and the other bacterial lineages.

Alpha-sarcin cleavage of ribosomal RNA is inhibited by the binding of elongation factor G or thiostrepton to the ribosome

The translocation reaction catalyzed by elongation factor G (EF-G) is inhibited either by alpha-sarcin cleavage of 23S rRNA or by the binding of thiostrepton to the E. coli ribosome. Here we show that the transitory binding of EF-G and GDP to the ribosome inhibited the rate of alpha-sarcin cleavage and that stabilization of this binding with fusidic acid completely prevented alpha-sarcin cleavage. A similar pattern of inhibition was seen upon the binding of elongation factor 2 to the S. cerevisiae ribosome. The irreversible binding of the antibiotic thiostrepton to the E. coli ribosome, on the other hand, decreased the rate of cleavage by alpha-sarcin approximately 2-fold. These results suggest that the alpha-sarcin site is located within the ribosomal domain for EF-G binding and that the conformation of this site is affected by the binding of thiostrepton.

Isolation and characterization of an inhibitor of ribosome-dependent GTP hydrolysis by elongation factor G

Two inhibitors of ribosome-dependent GTP hydrolysis by elongation factor (EF)G were found in the ribosome wash of Escherichia coli strain B. One of these inhibitors was purified to homogeneity and characterized. The isolated inhibitor was found to consist of two polypeptide subunits with apparent molecular masses of 23 kDa and 10 kDa. Inhibition of EF-G GTPase could not be overcome by increasing amounts of the elongation factor or high concentrations of GTP, but was reversed by large amounts of ribosomes. The effect of the inhibitor was reduced by increasing concentrations of either 30S or 50S ribosomal subunits. EF-G-dependent GTPase of 50S ribosomal subunits was not affected by the inhibitor. These findings clearly show that the inhibitor interferes with the modulation of EF-G GTPase activity by the interactions between 30S and 50S ribosomal subunits. Under conditions, where 30S CsCl core particles are able to associate with 50S subunits and to stimulate EF-G GTPase, the effect of the inhibitor was considerably reduced when intact 30S ribosomal subunits were substituted by 30S CsCl core particles. This finding indicates that 30S CsCl split proteins are important for the action of the inhibitor and that the inhibitor does not affect the EF-G GTPase merely by interfering with the association of ribosomal subunits. Furthermore, poly(U)-dependent poly(phenylalanine) synthesis was considerably less sensitive to the inhibitor than EF-G GTPase. When ribosomes were preincubated with poly(U) and Phe-tRNA(Phe), poly(phenylalanine) synthesis was considerably less affected by the inhibitor, whereas EF-G GTPase was still sensitive.

Purification and characterization of elongation factor G from bovine liver mitochondria

The mitochondrial protein synthesis translocase elongation factor Gmt (EF-Gmt) from bovine liver has been purified to greater than 90% homogeneity by a combination of conventional gravity and high performance liquid chromatography. The purification scheme results in an approximate overall 14,000-fold purification with 2% total recovery of EF-Gmt activity. Gel filtration chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicate that the mitochondrial factor is a single polypeptide with a molecular weight of 80,000. EF-Gmt displays similar levels of activity on its homologous mitochondrial ribosomes and on Escherichia coli ribosomes. The mitochondrial translocase is sensitive to temperatures above 37 degrees C, but the factor is partially protected from heat inactivation in the presence of GTP or GDP. The activity of EF-Gmt is inhibited by treatment of the factor with N-ethylmaleimide. In contrast to all other translocases tested to date, EF-Gmt is completely resistant to the inhibiting effect of fusidic acid when tested on its homologous ribosomes. It displays weak sensitivity to this antibiotic when assayed in the presence of heterologous E. coli ribosomes.

Stoichiometry of elongation factor G function in translation

A steady-state translation system has been used in vitro to measure the stoichiometry with which elongation factor G-GTP complexes are dissipated during polypeptide elongation. It has been possible to separate this dissipation from that associated with elongation factor Tu function. Our measurements for the wild-type as well as for two mutant variants indicate that there is one elongation factor G-GTP complex dissipated per peptide bond in the steady-state.

Novel mutants of elongation factor G

A novel mutant form of elongation factor G (EF-G) in Escherichia coli is described. This variant EF-G restricts reading frame errors by a factor of 2 to 3 in vivo at two different positions in a lacIZ fusion. In addition, a conventional fusidic acid resistant (fusR) mutant of EF-G was compared with the restrictive mutant. Both mutants were characterized in vitro in a steady-state poly(U) translating system. The data indicate that the restrictive EF-G variant has an altered interaction with the ribosome both in vivo and in vitro. In contrast, the conventional fusR variant is altered in its interaction with GTP, which is evident in vitro.

[Cloning and nucleotide sequence determination of the fus gene coding for the elongation factor G of Thermus thermophilus HB8]

A clone with the Thermus thermophilus HB8 fus gene coding for elongation factor G has been identified in a genomic library in plasmid pBR 322 by hybridization with labeled oligonucleotide 19 bases that are complementary in length to the 3'-end of the T. thermophilus fus gene. The fragment with the fus gene was recloned into the pTZ 18R plasmid. A restriction map of this fragment has been made. A set of short overlapping fragments of the fus gene has been obtained by nucleotide sequence unspecific linearization of the plasmid and by the restriction fragment subcloning into M13 mp18 and mp19 vectors. The nucleotide sequence of the fus gene was determined by the dideoxy chain termination method. Fus gene codes the elongation factor G 690 amino acids in length (Mr = 76756 Da). The amino acid sequence of EF-G from T. thermophilus has a 59.7% homology with that of E. coli and a 29.0% homology with EF-2 of rat liver.

Mapping of two promoters for elongation factor Tu within the structural gene for elongation factor G

The str operon of Escherichia coli contains the genes for ribosomal proteins S7 and S12 as well as elongation factors G and Tu (EF-G, EF-Tu). We have previously reported that there is a secondary promoter for expression of EF-Tu mapping within the upstream fus gene encoding EF-G (Zengel, J.M. and Lindahl, L. (1982) Mol. Gen. Genet. 185, 487-492) and have identified several potential promoter sequences within fus (Zengel, J.M., Archer, R.H. and Lindahl, L. (1984) Nucleic Acids Res. 12, 2181-2192). We have now further characterized this promoter activity. Measurements of transcription rates from various regions of the str operon in cells carrying the fus gene and the beginning of the tufA gene on a high copy number plasmid confirmed that transcription was initiated within a 600 bp EcoRI fragment in the distal portion of the fus gene. Furthermore, T1 nuclease mapping studies identified two 5' ends within this region, one about 400 bases upstream of tufA, the other about 270 bases upstream, suggesting that there are two tufA promoters within the fus gene. Both of these promoters are active in the intact chromosomal str operon.

Ribosomal RNA and protein mutants resistant to spectinomycin

We have compared the influence of spectinomycin (Spc) on individual partial reactions during the elongation phase of translation in vitro by wild-type and mutant ribosomes. The data show that the antibiotic specifically inhibits the elongation factor G (EF-G) cycle supported by wild-type ribosomes. In addition, we have reproduced the in vivo Spc resistant phenotype of relevant ribosome mutants in our in vitro translation system. In particular, three mutants with alterations at position 1192 in 16S rRNA as well as an rpsE mutant with an alteration of protein S5 were analysed. All of these ribosomal mutants confer a degree of Spc resistance for the EF-G cycle in vitro that is correlated with the degree of growth rate resistance to the antibiotic in culture.

Evolutionary relationship of archaebacteria, eubacteria, and eukaryotes inferred from phylogenetic trees of duplicated genes

All extant organisms are though to be classified into three primary kingdoms, eubacteria, eukaryotes, and archaebacteria. The molecular evolutionary studies on the origin and evolution of archaebacteria to date have been carried out by inferring a molecular phylogenetic tree of the primary kingdoms based on comparison of a single molecule from a variety of extant species. From such comparison, it was not possible to derive the exact evolutionary relationship among the primary kingdoms, because the root of the tree could not be determined uniquely. To overcome this difficulty, we compared a pair of duplicated genes, elongation factors Tu and G, and the alpha and beta subunits of ATPase, which are thought to have diverged by gene duplication before divergence of the primary kingdoms. Using each protein pair, we inferred a composite phylogenetic tree with two clusters corresponding to different proteins, from which the evolutionary relationship of the primary kingdoms is determined uniquely. The inferred composite trees reveal that archaebacteria are more closely related to eukaryotes than to eubacteria for all the cases. By bootstrap resamplings, this relationship is reproduced with probabilities of 0.96, 0.79, 1.0, and 1.0 for elongation factors Tu and G and for ATPase subunits alpha and beta, respectively. There are also several lines of evidence for the close sequence similarity between archaebacteria and eukaryotes. Thus we propose that this tree topology represents the general evolutionary relationship among the three primary kingdoms.

Effect of propan-2-ol on enzymic and structural properties of elongation factor G

Elongation factor G (EF-G) can support a GTPase activity in vitro even in the absence of ribosomes when propan-2-ol is present [GTPasep; De Vendittis, Masullo & Bocchini (1986) J. Biol. Chem. 261, 4445-4450]. In the present work the GTPasep activity of EF-G was further studied by investigating (i) the effect of ionic environment on GTPasep and (ii) the influence of propan-2-ol on the molecular structure of EF-G as determined by fluorescence and c.d. measurements. In the presence of 1-300 mM univalent cations (M+) alone, no detectable GTPasep activity was measured; however, in the presence of 1 mM-Mg2+ a considerable stimulation was observed at 40 mM-Li+ or 75 mM-NH4+. Among bivalent cations (M2+), 1 mM-Sr2+, 2-5 mM-Ca2+ and 1 mM-Ba2+ were the most effective, but, in the presence of 75 mM-NH4+, Mg2+ and Mn2+ became the most efficient, whereas the stimulation by other M2+ species was considerably decreased. C.d. measurements showed that the alcohol increased the mean molar residue ellipticity of EF-G at 285 nm, but not at 220 nm. As estimated from fluorescence measurements, in the presence of 20% (v/v) propan-2-ol the value of the dissociation constant of the complex formed between EF-G and 8-anilino-1-naphthalene-sulphonate decreased from 8 to 5 microM; similarly, the number of binding sites on EF-G for the fluorescent probe decreased from 13 to 6. Finally, the alcohol enhanced the quenching of the intrinsic fluorescence of EF-G caused by either acrylamide or KI. The data support the hypothesis that propan-2-ol induces moderate conformational changes of EF-G that make the catalytic centre accessible to the substrate even in the absence of ribosomes. Kinetics of GTPasep studied at different temperatures did not reveal additional structural changes of EF-G occurring with time or temperature.

Characterization of the str operon genes from Spirulina platensis and their evolutionary relationship to those of other prokaryotes

A 5.3 kb DNA segment containing the str operon (ca. 4.5 kb) of the cyanobacterium Spirulina platensis has been sequenced. The str operon includes the structural genes rpsL (ribosomal protein S12), rpsG (ribosomal protein S7), fus (translation elongation factor EF-G) and tuf (translation elongation factor EF-Tu). From the nucleotide sequence of this operon, the primary structures of the four gene products have been derived and compared with the available corresponding structures from eubacteria, archaebacteria and chloroplasts. Extensive homologies were found in almost all cases and in the order S12 greater than EF-Tu greater than EF-G greater than S7; the largest homologies were generally found between the cyanobacterial proteins and the corresponding chloroplast gene products. Overall codon usage in S. platensis was found to be rather unbiased.

Genes for the ribosomal proteins S12 and S7 and elongation factors EF-G and EF-Tu of the cyanobacterium, Anacystis nidulans: structural homology between 16S rRNA and S7 mRNA

A 6.5 kb region from the genome of the cyanobacterium, Anacystis nidulans 6301 was cloned using the tobacco chloroplast gene for ribosomal protein S12 as a probe. Sequence analysis revealed the presence of genes for ribosomal proteins S12 and S7 and elongation factors EF-G and EF-Tu in this DNA region. The arrangement is rps12 (124 codons) - 167 bp spacer - rps7 (156 codons) - 77 bp spacer - fus (694 codons) - 26 bp spacer - tufA (409 codons), which is similar to that of the Escherichia coli str operon. The deduced amino acid sequences of the A. nidulans S12 and EF-Tu show high homology (72%-82%) with the E. coli and chloroplast counterparts while those of the A. nidulans S7 and EF-G give low homology (51%-59%). Striking structural homology was found between the potential S7 binding region of 16S rRNA and the beginning of S7 mRNA, suggesting that feedback regulation of rps7 expression operates in A. nidulans.

Action of erythromycin and virginiamycin S on polypeptide synthesis in cell-free systems

Erythromycin (a 14-membered macrolide) and virginiamycin S (a type B synergimycin) block protein biosynthesis in bacteria, but are virtually inactive on poly(U)-directed poly(Phe) synthesis. We have recently shown, however, that these antibiotics inhibit the in vitro polypeptide synthesis directed by synthetic copolymers: this effect is analyzed further in the present work. We were unable to find any consistent alteration produced by these antibiotics on coupled and uncoupled EF-G- and EF-Tu-dependent GTPases, on the EF-Tu-directed binding of aminoacyl-tRNA to ribosomes, and on the EF-G- and GTP-mediated translocation of peptidyl-tRNA bound to poly(U,C).ribosome complexes. With these complexes, the peptidyl transfer reaction, as measured by peptidylpuromycin synthesis, was 10-30% inhibited by virginiamycin S and erythromycin. A direct relationship between the virginiamycin S- and erythromycin-promoted inhibition of poly(A,C)-directed polypeptide synthesis, on the one hand, and the EF-G concentration and the rate of the polymerization reaction, on the other hand, was observed, in agreement with a postulated reversible inhibitor action of these antibiotics. The increased inhibitory activity, which was observed during the first 4-6 rounds of elongation, in the presence of virginiamycin S or erythromycin, was suggestive of a specific action of these antibiotics on the correct positioning of peptidyl-tRNA at the P site. The marked stimulation of premature release of peptidyl-tRNA from poly(A,C).ribosome complexes can be referred to an altered interaction of the C-terminal aminoacyl residue of the growing peptidyl chain with the ribosome. We conclude that the action of virginiamycin S and erythromycin entails a template-dependent alteration of the interaction of peptidyl-tRNA with the donor site of peptidyltransferase, which may lead to a transient functional block of the ribosome and in some instances to a premature release of peptidyl-tRNA and termination of the elongation process.

The allosteric three-site model for the ribosomal elongation cycle. New insights into the inhibition mechanisms of aminoglycosides, thiostrepton, and viomycin

According to the allosteric three-site model for the ribosomal elongation cycle (Rheinberger, H.J. and Nierhaus, K.H. (1986) J. Biol. Chem. 261, 9133-9139), two types of A site (aminoacyl-tRNA site) occupation exist. First is the A site occupation after initiation (i-type), with only one site, the P site (peptidyl-tRNA site), being prefilled with a tRNA (initiator tRNA). Second is the A site occupation after an elongation cycle (e-type), with two prefilled sites, namely the P and E sites containing peptidyl-tRNA and deacylated tRNA, respectively. The individual reactions of the elongation cycle were tested, including both types of A site occupation in the presence of various antibiotics. A test system was used allowing the functional studies to be made with quantitative tRNA binding at 6 mM Mg2+. The following results were obtained: 1) thiostrepton (5 x 10(-6) M) induced a complete block of both EF-(elongation factor) G dependent and EF-G independent translocation, in agreement with older observations. The A-site occupation of the e-type was severely inhibited in contrast to that of the i-type. Thus, thiostrepton blocks the allosteric transitions in both directions, i.e. the transition from pre- to post-translocational state (translocation) and that from the post- to the pre-translocational state (A site occupation of the e-type). In addition the ribosomal binding of EF-G.[3H] GMPPNP was inhibited by about 60%. 2) Similarly, viomycin (5 x 10(-5) M) appears to be an inhibitor of both allosteric transitions, since it strongly inhibited the e-type (but not the i-type) A site occupation in addition to translocation. 3) The aminoglycosides streptomycin, hygromycin B, neomycin, kanamycin, and gentamicin prevented A site occupation of the e-type (residual activity below 15%). Neomycin and hygromycin, in addition, blocked the translocation reaction. Only marginal effects were observed with A site occupation of the i-type. It appears that the inhibition of the A site binding of the e-type (allosteric transition from the post- to the pretranslocational state) is the predominant effect of the misreading-inducing aminoglycosides.

Movable finite automata (MFA) models for biological systems. II: Protein biosynthesis

A recently introduced class of models, the Movable Finite Automata (MFA) models, are used for simulating the elongation of the polypeptide chain in protein biosynthesis. The results of these simulations, all carried out on a microcomputer, are given.

Interaction of elongation factors EF-G and EF-Tu with a conserved loop in 23S RNA

The elongation factors EF-Tu and EF-G interact with ribosomes during protein synthesis: EF-Tu presents incoming aminoacyl transfer RNA to the programmed ribosome as an EF-Tu-GTP-tRNA ternary complex and EF-G promotes translocation of peptidyl-tRNA and its associated messenger RNA from the A to the P site after peptidyl transfer. Both events are accompanied by ribosome-dependent GTP hydrolysis. Here we use chemical probes to investigate the possible interaction of these factors with ribosomal RNA in E. coli ribosomes. We observe EF-G-dependent footprints in vitro and in vivo around position 1,067 in domain II of 23S rRNA, and in the loop around position 2,660 in domain VI.EF-Tu gives an overlapping footprint in vitro at positions 2,655 and 2,661, but shows no effect at position 1,067. The 1,067 region is the site of interaction of the antibiotic thiostrepton, which prevents formation of the EF-G-GTP-ribosome complex and is a site for interaction with the GTPase-related protein L11 (ref. 3). The universally conserved loop in the 2,660 region is the site of attack by the RNA-directed cytotoxins alpha-sarcin and ricin, whose effects abolish translation and include the loss of elongation factor-dependent functions in eukaryotic ribosomes.

[Structural analysis of translating ribosomes. Proton magnetic resonance method]

Comparison has been made of the proton magnetic resonance (PMR) spectra of translating ribosomes in the pre-translocation and post-translocation states as well as of the complexes of translating ribosomes with elongation factors Tu (EF-Tu) or G (EF-G) in the presence of the uncleavable analogue of GTP--guanylyl-imidodiphosphate (GMP-PNP). It is shown that proteins L7/L12 within the translating ribosomes possess a high intramolecular mobility both in the pre-translocation and in the post-translocation states. The interaction of EF-G with translating ribosomes results in a decrease of the mobility of the L7/L12 proteins. The interaction of EF-Tu with translating ribosomes leads to slight changes in the PMR spectra different from the changes caused by EF-G.

Action of virginiamycin M on the stability of different ribosomal complexes to ultracentrifugation

It was previously shown that virginiamycin M produces in vivo an accumulation of pressure-sensitive (60 S) ribosomes, and in vitro an inactivation of the donor and acceptor sites of peptidyl transferase. The latter action, however, is expected to cause the accumulation in vivo of ribosome complexes carrying acylated tRNA species: such complexes are usually endowed with pressure resistance. However, present data indicate that poly(U).ribosome complexes carrying Phe-tRNA, Ac-Phe-tRNA or Ac-Phe-Phe-tRNA at either the A or the P site become pressure-sensitive after exposure to virginiamycin M in vitro. It is known also that uncoupled EF-G GTPase is stimulated by P-site-bound unacylated tRNA, not by the acylated species. Our data show, however, a stimulation of EF-G GTPase, when ribosomal complexes carrying Ac-Phe-tRNA or Ac-Phe-Phe-tRNA at the P site are incubated with virginiamycin M. The interpretation proposed to account for all these findings is that complexes carrying A- and P-site-bound aminoacyl-tRNA derivatives, which undergo a stable interaction with the peptidyl transferase, are endowed with ultracentrifugal stability, whereas complexes with unacylated tRNA (which does not interact with the enzyme) are pressure-sensitive. By inactivating the donor and acceptor sites of peptidyltransferase, virginiamycin M causes aminoacyl-tRNA.ribosome complexes to mimic tRNA.ribosome complexes in their pressure-lability and competence in EF-G GTPase stimulation. This interpretation is supported by the finding that the ribosome-promoted protection of aminoacyl-tRNA against spontaneous hydrolysis is suppressed by virginiamycin M.

Mutations in ribosomal proteins L7/L12 perturb EF-G and EF-Tu functions

In vitro cycling rates of E. coli ribosomes and of elongation factors EF-Tu and EF-G have been obtained and these are compatible with translation rates in vivo. We show that the rate of translocation is faster than 50 s-1 and therefore that the EF-G function is not a rate limiting step in protein synthesis. The in vivo phenotype of some L7/L12 mutants could be accounted for by perturbed EF-Tu as well as EF-G functions. The S12 mutants that we studied were, in contrast, only perturbed in their EF-Tu function, while their EF-G interaction was not impaired in relation to wild type ribosomes.

Synthesis of high-capacity immunoaffinity sorbents with oriented immobilized immunoglobulins or their Fab' fragments for isolation of proteins

Two methods for synthesizing high-capacity immunoaffinity sorbents on Sepharose and Separon HEMA E-1000 are described. The first is the oriented immobilization of monovalent immunoglobulin Fab fragments on a maleimide derivative of Sepharose via the formation of a covalent bond between the SH group of the Fab fragment at the C-terminus of the molecule and the maleimide covalently coupled to Sepharose. The second method is based on the oxidation of the immunoglobulin carbohydrate component, located in the Fc fragment, by periodate with subsequent immobilization of the derivatives on hydrazide derivatives of Sepharose or Separon. Sorbents for the isolation of monoclonal antibodies from the culture supernatants and the elongation factor EF-G from a crude extract of Escherichia coli cells were obtained. These sorbents are characterized by a high capacity, minimal non-specific sorption and high stability.