In Escherichia coli there is one binding site per ribosome for lincomycin, chloramphenicol and erythromycin.These antibiotics act at closely related sites on the 50‐S subunit. There are, however, some interesting differences in the properties of the three sites, such as: (a) the apparent possibility of obstructing the lincomycin site without closing the chloramphenicol site, (b) asymmetry of competition effects between chloramphenicol and erythromycin, (c) differential responses to ethanol and (d) differential responses to other antibiotics (puromycin, macrolides, streptogramins A and B and others also acting on the larger ribosome subunit).

G-factor interacts with the 50S ribo-somal subunit at a site which is distinct from the peptidyl transferase centre and which is inactivated by siomycin.

FEBS LettersVolume 7, Issue 2 p. 109-111 Full-length articleFree Access Interaction of Ac-Phe-tRNA with E. coli ribosomal subunits. 2. Resistance of the sparsomycin-induced complex to hydroxylamine action A. Jimenez, A. Jimenez Insituto de Biologia Celular, Velazquez, 144, Madrid-6, SpainSearch for more papers by this authorR.E. Monro, R.E. Monro Insituto de Biologia Celular, Velazquez, 144, Madrid-6, SpainSearch for more papers by this authorD. Vazquez, D. Vazquez Insituto de Biologia Celular, Velazquez, 144, Madrid-6, SpainSearch for more papers by this author A. Jimenez, A. Jimenez Insituto de Biologia Celular, Velazquez, 144, Madrid-6, SpainSearch for more papers by this authorR.E. Monro, R.E. Monro Insituto de Biologia Celular, Velazquez, 144, Madrid-6, SpainSearch for more papers by this authorD. Vazquez, D. Vazquez Insituto de Biologia Celular, Velazquez, 144, Madrid-6, SpainSearch for more papers by this author First published: April 02, 1970 https://doi.org/10.1016/0014-5793(70)80132-6Citations: 6AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References 1 A.E. Herner, I.H. Goldberg, L.B. Cohen, Biochemistry, 8, (1969), 1335– 2 A. Jimenez, R.E. Monro, D. Vazquez, FEBS Letters, 7, (1970), 103– 3 A. Jimenez, R.E. Monro, D. Vazquez, FEBS Letters, (1970), in press 4 R.E. Monro, M.L. Celma, D. Vazquez, Nature, 222, (1969), 356– 5 E. Davie, Methods Enzymol., 5, (1962), 719– 6 J. Lucas-Lenard, F. Lipmann, Proc. Natl. Acad. Sci. U.S., 57, (1967), 1050– 7 R.E. Monro, T. Staehelin, M.L. Celma, D. Vazquez, Cold Spring Harbor Symp. Quant. Biol., (1969), in press 8 E. Scolnick, G. Milman, M. Rosman, T. Caskey, Nature, 225, (1970), 152– 9 S. Pestka, Proc. Natl. Acad. Sci. U.S. in press. 10 R. Arlinghaus, R. Heintz, R. Schweet, Methods Enzymol., 12, (1968), 700– 11 S. Pestka, J. Biol. Chem., 242, (1967), 4939– 12 S. Bresler, R. Grajevskaja, S. Kirilov, E. Saminski, Biochim. Biophys. Acta, 155, (1968), 465– I. Rychlik, J. Černa, S. Chladek, J. Zemlicka, Z. Haladoya, J. Mol. Biol., 43, (1969), 13– Citing Literature Volume7, Issue2April 02, 1970Pages 109-111 ReferencesRelatedInformation

FEBS LettersVolume 7, Issue 2 p. 103-108 Full-length articleFree Access Interaction of Ac-Phe-tRNA with e. coli ribosomal subunits. 1. Sparsomycin-induced formation of a complex containing 50 S and 30 S subunits but not mRNA A. Jimenez, A. Jimenez Instituto de Biologia Celular, Velazquez 144, Madrid-6 SpainSearch for more papers by this authorR.E. Monro, R.E. Monro Instituto de Biologia Celular, Velazquez 144, Madrid-6 SpainSearch for more papers by this authorD. Vazquez, D. Vazquez Instituto de Biologia Celular, Velazquez 144, Madrid-6 SpainSearch for more papers by this author A. Jimenez, A. Jimenez Instituto de Biologia Celular, Velazquez 144, Madrid-6 SpainSearch for more papers by this authorR.E. Monro, R.E. Monro Instituto de Biologia Celular, Velazquez 144, Madrid-6 SpainSearch for more papers by this authorD. Vazquez, D. Vazquez Instituto de Biologia Celular, Velazquez 144, Madrid-6 SpainSearch for more papers by this author First published: April 02, 1970 https://doi.org/10.1016/0014-5793(70)80131-4Citations: 24AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume7, Issue2April 02, 1970Pages 103-108 ReferencesRelatedInformation

FEBS LettersVolume 6, Issue 3 p. 198-202 Full-length articleFree Access Catalysis of peptidyl transfer by human tonsil ribosomes and effects of some antibiotics R. Neth, R. Neth Instituto de Biología Celular, Velázquez, 144, Madrid -6, Spain Department of Pediatrics, University of Hamburg, Germany. Search for more papers by this authorR.E. Monro, R.E. Monro Instituto de Biología Celular, Velázquez, 144, Madrid -6, SpainSearch for more papers by this authorG. Heller, G. Heller Instituto de Biología Celular, Velázquez, 144, Madrid -6, Spain Department of Pediatrics, University of Hamburg, Germany. Search for more papers by this authorE. Battaner, E. Battaner Instituto de Biología Celular, Velázquez, 144, Madrid -6, SpainSearch for more papers by this authorD. Vazquez, D. Vazquez Instituto de Biología Celular, Velázquez, 144, Madrid -6, SpainSearch for more papers by this author R. Neth, R. Neth Instituto de Biología Celular, Velázquez, 144, Madrid -6, Spain Department of Pediatrics, University of Hamburg, Germany. Search for more papers by this authorR.E. Monro, R.E. Monro Instituto de Biología Celular, Velázquez, 144, Madrid -6, SpainSearch for more papers by this authorG. Heller, G. Heller Instituto de Biología Celular, Velázquez, 144, Madrid -6, Spain Department of Pediatrics, University of Hamburg, Germany. Search for more papers by this authorE. Battaner, E. Battaner Instituto de Biología Celular, Velázquez, 144, Madrid -6, SpainSearch for more papers by this authorD. Vazquez, D. Vazquez Instituto de Biología Celular, Velázquez, 144, Madrid -6, SpainSearch for more papers by this author First published: February 16, 1970 https://doi.org/10.1016/0014-5793(70)80056-4Citations: 47 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume6, Issue3February 16, 1970Pages 198-202 ReferencesRelatedInformation

Sparsomycin inhibits protein biosynthesis by inducing the formation of an inert complex between the peptidyl donor substrate and the 50S ribosomal subunit.

The way in which ribosomes are organized in Escherichia coli according to the translocation model [1–4 and refs. therein) to explain the overall reactions taking place in the biosynthesis of protein by E. coli ribosomes is shown in Fig. 1. It is well established that the direction of reading of mRNA is from the 5′ end to the 3′ end [5, 6]. The synthesis of bacterial protein is initiated with formyl-methionine [7, 8]. All the evidence so far suggests that the anticodon region of tRNA is recognized and its interaction with mRNA specifically stabilized by the 30 S subunit. Other portions of the tRNA and in particular the amino acid- or f-Met-bearing moiety interact with the 50 S subunit. According to the one entry site theory of the translocation model, now the most accepted one, the f-Met-tRNAf binds initially at the “A” site and is then translocated to the “P” site (Fig. la) leaving the “A” site open for the AA 1-tBNA1 to enter (Fig. lb) [4B, 9, 10]. According to the two entry sites variant of the translocation model, the chain is initiated by direct entry of f-Met-tRNAf at the “P” site, whereas during chain growth aminoacyl-tRNA binds at the “A” site [11–13]. The specificity for the initiating role of f-Met-tRNAf and its binding to the “P” site is due to the α-NH2 of the methionine being blocked by formylation, and to the unique structure of the tRNAf.

The peptide bond-forming reaction of protein synthesis is catalyzed by the larger ribosomal subunit (Monro, 1967; Maden, Traut, and Monro, 1968) (Fig. 1). It has been postulated that the reaction is effected by a catalytic center similar to the active centers of soluble enzymes, but different in being part of the ribosome, which is a kind of "super-enzyme" with several distinct but mutually integrated functional centers (Monro, Maden, and Traut, 1967). The catalytic center was termed peptidyl transferase (as opposed to peptide synthetase, which is a misnomer) in accordance with standard enzyme nomenclature. The present paper surveys past and present work on the peptidyl transferase center of E. coli ribosomes. Studies with ribosomes from higher organisms are surveyed in another paper in this volume (Vazquez, Battaner, Neth, Heller, and Monro).

Isolated 5OS ribosomal subunits can be induced to catalyse polymerization of aminoacyl-tRNA in absence of template and 30S subunits.

It is well established that peptide bond formation during protein synthesis in E. coli is catalyzed by the 50 S ribosomal subunit and it has been proposed that the catalytic agent is an enzyme, peptidyl transferase, integrated into the subunit structure (Monro, Staehelin, Celma, and Vazquez, this volume). 70 S ribosomes from other bacterial species have been shown to be very similar to those of E. coli in this respect (Vazquez, Celma, Fernandez-Muñoz, and Monro, unpubl.), but corresponding studies have not hitherto been reported with 80 S ribosomes. Indeed, it has been widely believed since the work of Arlinghaus, Schaeffer,and Schweet (1964), that a supernatant protein, TF-1, is responsible for catalysis of peptide bond formation in mammalian cytoplasm. However, it has been suggested that the reaction might be ribosome-catalyzed in view of the reactivity with puromycin of nascent protein on washed 80 S ribosomes from rat liver (Skogerson and Moldave,...

The enormous complexity of ribosome structure even in simple organisms such as bacteria has become fully evident during the last few years. Most of the detailed information on the chemical aspects of ribosomal proteins has been obtained from the 30 S ribosome of Escherichia coli (Traut et al., 1967; Moore et al., 1968; Fogel and Sypherd, 1968; Delius and Traut, 1969; Traut et al., this volume; Kurland et al., this volume). The functional aspects and how they relate to the structural complexity of the 30 S ribosome have been studied to a most remarkable degree of detail in Nomura's laboratory (this volume and Traub et al., 1967, 1968b, 1969; Ozaki et al., 1969). Although some protein components are of particular importance for specific functions of the 30 S ribosome (chain initiation, codon specific aminoacyl-transfer RNA (tRNA) binding, fidelity of coding) it is quite clear that the functions of many proteins...

Effects of cations and pH value on ribosome‐catalyzed peptidyl transfer were studied, using as assays the reaction of puromycin with (a) washed, polyphenylalanine‐charged Escherichia coli ribosomes and (b) terminal fragments from formlyl‐methionyl‐tRNA (CAACCA‐Met‐F and CCA‐Met‐F) in the presence of purified 50 S ribosomal subunits. In both systems the reaction required the presence of suitable divalent and monovalent cations, and was progressively inhibited below pH 8.5.In the polyphenylalanine system Mg2+ was active over the range 0.3 mM to 1 M, with a broad optimum from approximately 3 to 100 mM. Mg2+ was replaceable by Ca2+ or Mn2+. Other divalent metal ions were inert or inhibitory. Spermidine was also inert. Monovalent cations were active in the order, NH4+ > K+= Rb+ > Cs+. NH4+ and K+ were progressively more effective from 10 mM to at least 1 M. Na+ and Li+ were inert.The reaction of formyl‐methionyl oligonucleotides with puromycin showed similar responses to the polyphenylalanine system except that (a) Mg2+ was active over the range 5 mM to 1 M with an optimum at approximately 100 mM, (b) Ca2+ was inert, (c) K+ was inactive below 100 mM, and (d) NH4+ was only weakly active.The bearing of the results on the mechanism of ribosome‐catalyzed peptidyl transfer is discussed, and a possible application of the results is noted.

The reaction of puromycin with polyphenylalanine-charged Escherichia coli ribosomes has been characterized. Release of polyphenylalanine from transfer RNA was estimated by a new, rapid method based on differential solubilities of substrate and product in m-cresol. Occurrence of a reaction in the absence of supernatant and GTP was demonstrated with (a) polyphenylalanine-charged 70 s ribosomes which had been washed with salt solution under conditions similar to those used for removing the supernatant factors of protein synthesis, and (b) purified, polyphenylalanine-charged 50 s subunits. Only monovalent and divalent cations and buffer are required for this “supernatant-independent” reaction, and under suitable conditions 70 to 80% of the polyphenylalanine is released from transfer RNA. Evidence from these and other results indicates that the puromycin reaction takes place by the same mechanism as peptide bond formation in protein synthesis, and that peptide bond formation is catalysed by the 50 s ribosomal subunit and does not directly involve supernatant factors or GTP. The reaction has characteristics typical of enzyme reactions, and the catalytic agent has been named “peptidyl transferase”. Kinetics of the supernatant-independent reaction are heterogeneous. A fraction of the charged ribosomes is highly reactive and may represent a preformed enzyme-substrate complex. Effects of puromycin concentration and various other factors on the kinetics are described. The reaction is inhibited by addition of 4 m-urea or 0·5% sodium dodecyl sulphate, by prior heating of charged ribosomes to 70°C, and by pre-treatment with 0·5 to 2% formaldehyde. The principle findings with 70 s ribosomes were confirmed with isolated, poly-phenylalanine-charged 50 s subunits.

F-Met or Met-F, N'-formyl-methionyl; Ac- or -Ac, N'-acetyl; P-site and A-site, the respective sites on the ribosome with which peptidyl-tRNA and aminoacyl-tRNA are associated at the moment of the peptidyl transfer reaction.

In this work, the structural, electronic and absorption properties of crystalline 3′-Amino-3′-deoxyadenosine (3′-AD) under hydrostatic compression of 0–300 GPa have been studied by using density functional theory with dispersion correction. The crystal structure of 3′-AD was relaxed using three types of exchange correlation energy and two types of van der Waals corrections at ambient conditions. The results indicate that PBE-TS is the best functional for studying 3′-AD. In addition, the c-direction is much stiffer than the a- and b-axis at 0–150 GPa, suggesting the 3′-AD crystal is anisotropic in the certain pressure region. Besides, pressured-induced formations of covalent bonds in P1 and P1z molecules results the formation of new four-atom ring at 110 GPa, and new five-atom ring at 290 GPa, resceptively. Then, the analysis of the band gap and DOS (PDOS) of 3′-AD indicate that its electronic character changes from insulator at 90 GPa into semiconductor, but the electron transition is much different at 110 GPa. Moreover, the relatively high optical activity with the pressure increases of 3′-AD is seen from the absorption coefficients, and two obvious structural transformations are also observed at 50 GPa and 100 GPa, respectively.

We characterize amorphous solid dispersions (ASDs) of the Chloramphenicol antibiotic in two biodegradable polylactic acid polymers, namely a commercial sample of enantiomeric pure PLLA and a home-synthesized PDLLA copolymer, investigating in particular the effect of polylactic acid in stabilizing the amorphous form of the drug and controlling its release (e.g. for antitumoral purposes). Broadband dielectric spectroscopy and differential scanning calorimetry are employed to study the homogeneity, glass transition temperature and relaxation dynamics of solvent-casted ASD membranes with different drug concentrations. We observe improved physical stability of the ASDs with respect to the pure drug, as well as a plasticizing effect of the antibiotic on the polymer, well described by the Gordon-Taylor equation. The release of the active pharmaceutical ingredient from the films in a simulated body fluid is studied by UV/vis spectroscopy at two different drug concentrations (5 and 20% in weight). The amount of released drug is found to be proportional to the square root of time, with proportionality constant that is almost the same in both dispersions, despite the fact that the relaxation time and thus the viscosity of the two samples differ by four orders of magnitude at body temperature. Since the drug release kinetics does not display a significant dependence on the drug content in the carrier, it may be expected to remain roughly constant during longer release times.

Peptide bond formation on the ribosome takes place in an active site composed of RNA. Recent progress of structural, biochemical, and computational approaches has provided a fairly detailed picture of the catalytic mechanism of the reaction. The ribosome accelerates peptide bond formation by lowering the activation entropy of the reaction due to positioning the two substrates, ordering water in the active site, and providing an electrostatic network that stabilizes the reaction intermediates. Proton transfer during the reaction appears to be promoted by a concerted proton shuttle mechanism that involves ribose hydroxyl groups on the tRNA substrate.