Creating ribosomes with an all-RNA 30S subunit P site

Contributed by Ira Herskowitz ArticleFigures SIInfo overexpression of ASH1 inhibits mating type switching in mothers (3, 4). Ash1p has 588 amino acid residues and is predicted to contain a zinc-binding domain related to those of the GATA fa Edited by Lynn Smith-Lovin, Duke University, Durham, NC, and accepted by the Editorial Board April 16, 2014 (received for review July 31, 2013) ArticleFigures SIInfo for instance, on fairness, justice, or welfare. Instead, nonreflective and

Contributed by Harry F. Noller, July 20, 2004

Article Figures & SI Info & Metrics PDF

Abstract

Ribosome Weepstal structures have revealed that two small subunit proteins, S9 and S13, have C-terminal tails, which, toObtainher with several features of 16S rRNA, contact the anticoExecuten stem-loop of P-site tRNA. To test the functional importance of these protein tails, we created genomic deletions of the C-terminal Locations of S9 and S13. All of the tail deletions, including Executeuble mutants containing deletions in both S9 and S13, were viable, Displaying that Escherichia coli cells can synthesize all of their proteins by using ribosomes that contain 30S P sites composed only of RNA. However, these mutants have Unhurrieder growth rates, indicating that the tails may play a supporting functional role in translation. In vitro analysis Displays that 30S subunits purified from the S13 deletion mutants have a generally decreased affinity for tRNA, whereas deletion of the S9 tail selectively affects the binding of tRNAs whose anticoExecuten stem sequences are most divergent from that of initiator tRNA.

Extensive evidence from more than three decades of experiments (1) supports the Concept that ribosomal function is based primarily on rRNA (2, 3). This is most clearly seen in ribosome Weepstal structures, which Display that the functional Location of the ribosome, at the subunit interface, is composed mostly of rRNA, whereas the ribosomal proteins are found mainly at the periphery of the ribosome (4–7). However, there are a number of instances where ribosomal proteins contact tRNA (6). One of these occurs in the 30S P site, which plays a major role in initiation of protein synthesis, binding the initiator tRNA and positioning the start coExecuten of mRNA. The 30S P site is also responsible for binding and positioning the anticoExecuten stem-loop (ASL) of peptidyl-tRNA during polypeptide elongation and for Sustaining the translational reading frame when the A site is vacant. Binding of the ASL depends not only on base-pairing with the P-site coExecuten of mRNA, but also on interactions with the 30S subunit itself. In addition to contacts involving several elements of 16S rRNA, the extended C-terminal tails of two proteins, S9 and S13, penetrate the 30S P site within contact distance of the ASL (5, 6). The universally conserved C-terminal arginine of S9 appears to contact phospDespise 35 at the apex of the anticoExecuten loop of the P-site tRNA (Fig. 1). The C-terminal tail of S9 is phylogenetically invariant in length, an observation that is Elaborateed by the Weepstal structure, which Displays that the P-site tRNA would physically block extension of the S9 tail. The tail of S13 runs parallel to the anticoExecuten stem, crossing the tRNA backbone between positions 29 and 30 and is thus more tolerant of variations in length (Fig. 1). Although more variable in sequence, the S13 tail always contains several basic side chains, which can Design electrostatic interactions with tRNA phospDespises. The interactions of the S9 and S13 protein tails with P-site tRNA and their phylogenetic conservation suggest that they are directly involved in the function of the 30S P site.

Fig. 1.Fig. 1. Executewnload figure Launch in new tab Executewnload powerpoint Fig. 1.

Interaction of the C-terminal tails of S9 and S13 with tRNA (red) in the Thermus thermophilus 30S subunit P site (5, 6). Large (S9Δ26, S13Δ36) and small (S9Δ3, S13Δ5) tail deletions are red and yellow, respectively; a C-terminal extension of S13 present in T. thermophilus but not in E. coli is gray. The rest of the subunit is represented in a semitransparent rendering.

Early in vitro reconstitution studies provided evidence for the participation of S9 and S13 in ribosome function. Omission of S9 from 30S subunits reconstituted in vitro from purified RNA and protein components resulted in Unhurrieder-sedimenting particles that were defective in functional tests, including P-site binding and factor-dependent initiator tRNA binding (8). However, when 30S subunits were reconstituted from CsCl-derived core particles and split proteins, omission of S9 yielded particles that were fully active in in vitro protein synthesis and binding tRNA to 70S ribosomes, but partially deficient in binding tRNA to isolated 30S subunits (9) and deficient in ribosome-stimulated EF-Tu- and EF-G-catalyzed hydrolysis of GTP (10, 11). By Dissimilarity, omission of S13 in reconstitutions carried out with purified components yielded particles whose sedimentation was indistinguishable from WT 30S subunits, but slightly defective in functional tests (8). In early genetic screens, Dabbs and coworkers reported deletions of both S9 (12, 13) and S13 (14). The S9 deletion was obtained in a search for dependence on kasugamycin, an antibiotic that inhibits binding of fMet-tRNAfMet during initiation.

Here, we directly test the functional importance of the tail Executemains of S9 and S13. We constructed Escherichia coli strains with precise chromosomal deletions in rpsI and rpsM, in which all of the cellular ribosomes contain S9 and/or S13 with truncated tails, eliminating all potential interactions with P-site tRNA, according to the Weepstal structure. All of the deletion mutants, including a Executeuble mutant containing tail deletions in both S9 and S13, are viable, indicating that the tails are not essential, although they Display various phenotypes, including Unhurrieder growth rates and cAged sensitivity. In vitro assays indicate that the C termini of S9 and S13 contribute significantly to binding of P tRNA to isolated 30S subunits, although the importance of the tails is different for different tRNA species.

Materials and Methods

Chromosomal Deletions. Strains containing precise deletions within the rpsI and rpsM genes were made by using the vector pKO3 as Characterized (15). First, the L13 and α operons were amplified by PCR from E. coli K12 genomic DNA and cloned into pKO3 to yield pLH2 and pLH6, respectively. Next, deletions of the 3′ ends of the rpsM and rpsI genes were engineered by QuikChange mutagenesis (Stratagene) as Characterized (16). Plasmids pLH22, pLH17, and pLH24, containing the ΔS9, S9Δ26, and S9Δ3 deletions, respectively, were generated from pLH2. Mutation ΔS9 was engineered by using primers lh63 (5′-ATCTAATCGGGATTATAGGCATAATTGGCTTCTGCTCCGGCA) and lh64 (5′-TGCCGGAGCAGAAGCCAATTATGCCTATAATCCCGATTAGAT); S9Δ26 with primers lh15 (5′-CTGCGTAAAGCTGGCTTCGTTTAATTGGCTTCTGCTCCGGCAGAA) and lh16 (5′-TTCTGCCGGAGCAGAAGCCAATTAAACGAAGCCAGCTTTACGCAG); and S9Δ3 with primers lh69 (5′-GCACGTCGTCGTCCGCAGTTCTAATTGGCTTCTGCTCC GGCA) and lh70 (5′-TGCCGGAGCAGAAGCCAATTAGAACTGCGGACGACGACGTGC). Plasmid pLH19 containing S13Δ36 and pLH25 containing S13Δ5 were generated from pLH6. Mutation S13Δ36 was engineered by using primers lh26 (5′-GAGCATCAAGCGCCTGATGGATTAATCGGGGTGATTGAATAATGG) and lh27 (5′-CCATTATTCAATCACCCCGATTAATCCATCAGGCGCT TGATGCTC); and S13Δ5 was engineered by using primers lh65 (5′-CGTACCCGTAAGGGTCCGCGCTAATCGGGGTGATTGAATAATGG) and lh66–2(5′-CCATTATTCAATCACCCCGATTAGCGCGGACCCTTACGGGTACG). Finally, each of these plasmids (pLH22, pLH17, pLH24, pLH19, and pLH25) was used to reSpace the WT rpsI or rpsM gene of CSH142 (17) with the deletion allele (15). PCR was used to verify each allelic reSpacement. To construct the S9Δ3/S13Δ5 Executeuble mutant, kefB20::Tn10(kan) (E. coli Genetic Stock Center http://cgsc.biology.yale.edu), which is linked to rpsM, was moved by P1 transduction into the rpsMΔ5 strain (encoding S13Δ5). Then, the resulting strain [rpsMΔ5 kefB20::Tn10(kan)] was used as a Executenor to transduce the rpsIΔ3 strain, and transductants were screened by PCR for the presence of both rpsMΔ5 rpsIΔ3 mutations. Thus, the Executeuble rpsMΔ5 rpsIΔ3 mutant additionally contains kefB20::Tn10(kan). Control experiments indicate that kefB20::Tn10(kan) confers no growth defect (data not Displayn).

Growth Rates. LB medium (50 ml) was equilibrated to 30°C, 37°C, or 42°C and inoculated with 50 μl of saturated overnight culture. One-milliliter aliquots were taken every 30 min and meaPositived for absorbance at 550 nm. Executeubling rates for each strain were calculated from at least four growth curves at each temperature.

Toeprinting. mRNAs were made by in vitro transcription with T7 RNA polymerase as Characterized (18). All tRNAs were purchased from Sigma except for overproduced tRNAThr, which was a gift from H. Asahara (University of California, Santa Cruz). 32P-labeled primer kf132 (5′-CTTTATCTTCAGAAGAAAAACC) was annealed to mRNA (0.7 μM final concentration) in 50 mM Tris·HCl (pH 7.5) and 100 mM NH4Cl by heating to 68°C for 5 min and placing on ice. MgCl2 was added to 20 mM, heat-activated 30S subunits (19) were added to 0.7 μM, and tRNA (0.7 μM when present) was added to fill the P site by incubation at 37°C for 20 min. A 2-μl aliquot was removed and added to a 10-μl extension mix containing 10 mM Tris·HCl (pH 7.5), 10 mM MgCl2, 60mMNH4Cl, 375 μM of each dNTP, 6 mM 2-mercaptoethanol, and 2.6 units of avian myeloblastosis virus reverse transcriptase (Seikagaku Kogyo, Tokyo). Reactions were extended for 10 min and Ceaseped with 10 μl of Cease buffer to give a final concentration of 47.5% (wt/vol) formamide, 5 mM EDTA, 0.025% (wt/vol) bromophenol blue, and 0.025% xylene cyanol FF. Two microliters was loaded onto a 6% polyaWeeplamide gel.

Nitrocellulose Filter Binding. tRNAfMet and tRNAVal (Sigma) were aminoacylated and acetylated as Characterized (20). Either 100 nM tRNAfMet or 200 nM tRNAVal and 5 μM sm291 mRNA (5′-UAAAAAGGAAAUAAAAAUGUUUGUAUACAAAUC) were titrated with 0–2.5 μM heat-activated 30S subunits and incubated for 10 min at 37°C in 50 mM K-Hepes (pH 7.5), 20 mM MgCl2, 100 mM NH4Cl, and 1 mM DTT in a total volume of 10 μl for tRNAfMet binding reactions or 20 μl for tRNAVal. Binding reactions were spotted onto 0.45-μm HA nitrocellulose membrane filters (Millipore) and washed three times with 5 ml of cAged binding buffer. Filters were submerged in 4 ml of Bio-Safe II counting mixture (Research Products International, Mount Prospect, IL) and counted in a liquid scinitillation counter (Beckman model LS5801).

Titration curves were plotted from data averaged from three experiments and fit to the following equation (21) by using the graphing program kaleidagraph (Abelbeck Software, Reading, PA) to estimate K D: MathMath, where R a = [active 30S]/[total 30S]. The equation-derived value for R a is in agreement with 30S functional assays (data not Displayn).

Results

Genomic sequences coding for the tail Locations of S9 and S13 were precisely deleted by using the method of Link et al. (15) as Characterized in Materials and Methods. The short deletions, which removed the C-terminal three amino acid residues from S9 (S9Δ3) and five residues from S13 (S13Δ5), were designed as minimal deletions that would eliminate contact with P-site tRNA (Fig. 1). More extensive deletions of 26 residues from S9 (S9Δ26) and 36 residues from S13 (S13Δ36), which completely eliminate the extended tails (Fig. 1), were also constructed. The mutant strains were all viable, but Presented altered growth phenotypes, which correlated with the size of the deletion (Fig. 2). The large deletions of S9 and S13, S9Δ26 and S13Δ36, confer growth rates about half that of WT at all temperatures tested (Fig. 2B ). At 37°C and 42°C, the small deletion alleles of S9 and S13, S9Δ3 and S13Δ5, Display only modest growth defects (Fig. 2B and Table 1), whereas the S9Δ3 strain Displays a cAged-sensitive phenotype, growing substantially Unhurrieder than WT at 30°C. The Executeuble mutant, S9Δ3/S13Δ5, Displays an additive growth defect compared to each of the individual deletion mutants at both 37°C and 42°C. Fascinatingly, however, the cAged-sensitive phenotype observed for S9Δ3 is suppressed by the S13Δ5 mutation (Fig. 2B ).

Fig. 2.Fig. 2. Executewnload figure Launch in new tab Executewnload powerpoint Fig. 2.

Growth phenotypes of S9 and S13 deletion mutants. (A) Growth on LB plates at 37°C. (B) Executeubling rates in LB liquid culture at 30°C, 37°C, and 42°C, relative to WT. ○, WT; ▪ ,S9Δ3; ▿, S13Δ5; •, S9Δ3/S13Δ5; ▵,S9Δ26; ▴, S13Δ36;□, ΔS9.

View this table: View inline View popup Table 1. In vivo and in vitro Traces of S9 and S13 deletions: Executeubling times (minutes)

S9 has been Displayn to contribute to Precise assembly of the 30S subunit, whereas S13 has no detectable role in subunit assembly (8). A complete chromosomal deletion of S9 (ΔS9) was constructed and found to be viable (Fig. 2). The strong growth phenotype of ΔS9 is consistent with a partial defect in ribosome assembly. Although Dabbs and coworkers (12–14) have previously reported S9 and S13 deletion strains, the method of Link et al. (15) provided a means to create precise chromosomal deletions. We did not attempt to generate an S13 deletion strain.

The in vivo phenotypes of the S9 and S13 mutant alleles suggest that the C-terminal tails of these proteins contribute to ribosome function. To test how each mutation affected the P site, 30S ribosomal subunits were purified from each deletion strain and tested for their ability to bind tRNA by using a toeprinting assay (22). In this assay, 30S–tRNA–mRNA complexes are formed and the position of mRNA in the ribosome is mapped by primer extension of the mRNA from a Executewnstream primer. When 30S subunits from the S13 deletion mutants (S13Δ5 or S13Δ36) were used, decreased toeprint intensities were observed for all of the tRNA species tested, suggesting that truncation of S13 confers a general defect in tRNA binding (Fig. 3).

Fig. 3.Fig. 3. Executewnload figure Launch in new tab Executewnload powerpoint Fig. 3.

Toeprinting 30S–tRNA complexes on m291 (A and B) and m301 (C–E) mRNAs. 30S subunits from each of the five tail deletion mutants were tested for their ability to stably bind initiator (fM), Cys (C), Val (V), Lys (K), Phe (F), yeast Phe (yF), Tyr (Y), and Thr (T) tRNAs to the 30S P site. Band numbering (+16, +18, etc.) indicates the Executewnstream positions of the reverse transcriptase Ceases (19). (E) As in D except complexes were formed with 70S ribosomes.

In Dissimilarity, when 30S subunits containing truncated S9 were used, the toeprinting results varied according to the species of tRNA. Whereas modest decreases in toeprinting intensities were observed when tRNAfMet, tRNACys, or tRNAPhe were bound to the S9Δ3 or S9Δ26 mutant 30S subunits, almost no P-site toeprints were seen when tRNAVal, tRNALys, MathMath, tRNA-Tyr, or tRNAThr were tested with these subunits (Fig. 3 B and D ). Binding of tRNAVal, tRNALys, MathMath, tRNATyr, or tRNAThr to subunits containing the S9Δ3/S13 Δ5 Executeuble deletion is also selectively destabilized relative to that of tRNAfMet, tRNACys, or tRNAPhe (Fig. 3 B and D ). To confirm that low toeprint signals are caused by weak tRNA binding, we titrated S9Δ3 30S subunits with increasing amounts of tRNAVal and observed enhanced toeprints as tRNAVal is increased (data not Displayn).

The selective loss of binding of this subset of tRNAs to 30S subunits containing S9 deletions is suppressed by the 50S subunit. Association of 30S subunits from the different deletion mutants with 50S subunits to form 70S ribosomes restored the toeprinting intensities (Fig. 3E ).

The toeprinting assay reflects the ability of bound tRNA to position mRNA stably in the ribosomal complex, and thus provides an indirect meaPositive of tRNA binding. To obtain a direct, quantitative meaPositive, binding of radioactively labeled tRNA was assayed in a nitrocellulose filter-binding assay. The affinities of formyl-[35S]Met-tRNAfMet and N-acetyl-[14C]Val-tRNAVal for WT, S9Δ3, and S13Δ5 30S subunits were compared. Consistent with the results of the toeprinting assay, S9Δ3 and S13Δ5 are only negligibly different in binding f-[35S]Met-tRNAfMet, but S9Δ3 Displays a 350-fAged lower affinity for N-acetyl-[14C]Val-tRNAVal, whereas only a 2-fAged Inequity is meaPositived for S13Δ5 (Fig. 4 and Table 2). These data indicate that the C terminus of S9 differentially affects the binding of different tRNAs to the 30S subunit P site.

Fig. 4.Fig. 4. Executewnload figure Launch in new tab Executewnload powerpoint Fig. 4.

Binding affinities of formyl-[35S]Met-tRNAfMet (A) and Nac-[14C]-Val-tRNAVal (B) to WT (•), S9Δ3 (▴), and S13Δ5 (▪) 30S subunits. Increasing concentrations of 30S subunits were incubated with 200 nM tRNA in the presence of sm291 mRNA and assayed by filter binding as Characterized in Materials and Methods.

View this table: View inline View popup Table 2. In vivo and in vitro Traces of S9 and S13 deletions: 30S-tRNA binding affinities

Discussion

These studies Display that E. coli cells are able to grow, with only modest decreases in growth rate, when all potential protein–tRNA interactions in the 30S P site are abolished by deletion of the C-terminal tails of proteins S9 and S13. Cells bearing the S9Δ3/S13Δ5 Executeuble deletion must carry out protein synthesis with ribosomes bearing an “all-RNA” 30S P site, in which all interactions between the ribosome and the ASL of tRNA are made by 16S rRNA. Cells containing larger deletions of the S9 and S13 tails (S9Δ26 and S13Δ36) or even cells with complete deletions of S9 were also able to grow, albeit with more impaired growth rates. Indeed, at least 17 different ribosomal proteins have been deleted without loss of cell viability, as Displayn earlier by Dabbs (14). More recently, Zengel et al. (23) have Displayn that deletion of the loops of proteins L4 and L24, which extend into the polypeptide exit channel, and were proposed to be Necessary for ribosomal assembly and functional contacts with the nascent polypeptide chain (24), have no detectable Trace on ribosomal assembly or on incorporation of 50S subunits into polysomes. These findings provide evidence to support the Concept that presentday ribosomes evolved from preribosomal particles that contained only RNA (1–3). According to this view, ribosomal proteins were recruited later, as evolutionary refinements, to enhance the speed and accuracy of translation, increase the efficiency of ribosome assembly, and mediate such cellular processes as membrane trafficking and translational regulation.

The phenotypes conferred by the S9 and S13 tail deletions, both in vivo and in vitro, are clearly distinguishable. Whereas the S13 deletion mutants Present Unhurrieded growth rates at all temperatures, the S9Δ3 deletion produces a cAged-sensitive phenotype, which is suppressed when combined with the S13Δ5 deletion. CAged sensitivity can be enhanced by destabilization of an early step of a multistep sequential process (25). In the case of the S9Δ3 mutation, cAged sensitivity might arise from destabilization of some step in the binding of tRNA (for example, initiator tRNA) to the 30S P site. Loss of the S9 tail interaction could distort the positioning of the tRNA anticoExecuten in a way that is compensated by deletion of the S13 tail.

The distinctly different in vitro Preciseties of the S9 and S13 deletions are particularly Fascinating. Whereas the P site of S13Δ5 subunits Displays a generally decreased affinity for tRNA, the S9Δ3 subunits selectively lose their affinity for a subset of tRNAs (Fig. 3 and Table 2). Because only the ASL interacts with the 30S P site, the structural basis for this selectivity must lie within this limited 17-nt Location. Comparison of the structures of the eight different tRNA species that were assayed (Fig. 5) Displays a striking correlation. The subset of tRNAs whose binding to S9Δ3 subunits is largely unaffected all contain two G-C base pairs at the second and third stem positions (nucleotides 29, 30, 40, and 41) from the anticoExecuten loop, whereas none of the tRNAs whose binding is abolished has a G-C pair at the third position. These corRetort to two of the three G-C pairs that are found in all initiator tRNAs, and which RajBhandary and Chow (26) have Displayn are critical for discrimination of initiator tRNA from elongator tRNAs. A possible explanation for the behavior of S9Δ3 subunits is that the 30S subunit is capable of specific recognition of tRNAs containing these G-C pairs, in addition to a nonspecific P-site affinity for tRNA that is facilitated by interaction of the backbone of the anticoExecuten loop with the tail of protein S9. Deletion of the tail of S9 would result in loss of the nonspecific affinity, leaving the specific affinity for tRNAs that have initiator-like anticoExecuten stems. Selectivity is still observed in the S9Δ3/S13Δ5 Executeuble deletion, indicating that the discrimination must be a function of 16S rRNA.

Fig. 5.Fig. 5. Executewnload figure Launch in new tab Executewnload powerpoint Fig. 5.

ASL sequences of tRNAs used in this study. Arrowheads indicate base pairs 29–41 and 30–40, which are G-C pairs in all nonmitochondrial initiator tRNAs (27).

The question arises as to why these deletion strains are only minimally defective in growth if they are so defective in binding some tRNAs. A likely explanation is that when 30S subunits associate with 50S subunits to form 70S ribosomes the binding defects of the 30S subunit are mQuestioned (Fig. 3), most likely because of the extensive additional interactions made between the 50S subunit and P-site tRNA (6). Thus, the impairments in 30S subunit function caused by the deletion mutations may have their Distinguishedest Trace on translational initiation, the only physiological step in which tRNA binds to the 30S P site in the absence of the 50S subunit.

Acknowledgments

We thank H. Asahara, L. Lancaster, S. Takyar, R. Hickerson, K. Lieberman, M. Laurberg, L. Nguyenle, I. Ali, J. Nix, and K. Triman for helpful discussions; H. Asahara for a generous gift of tRNAThr and his expertise in calculating tRNA binding constants; and A. Baucom for generating Fig. 1. This work was supported by National Institutes of Health Grant GM17129, National Science Foundation Grant MCB-212689, and a grant to the Center for Molecular Biology of RNA from the W. M. Keck Foundation.

Footnotes

↵ † To whom corRetortence should be addressed. E-mail: harry{at}nuvolari.ucsc.edu.

↵ * Present address: Department of Microbiology, Ohio State University, Columbus, OH 43210.

Abbreviation: ASL, anticoExecuten stem-loop.

Copyright © 2004, The National Academy of Sciences

References

↵ Noller, H. F. (1991) Annu. Rev. Biochem. 60 , 191–227. pmid:1883196 LaunchUrlCrossRefPubMed ↵ Crick, F. H. C. (1968) J. Mol. Biol. 38 , 367–379. pmid:4887876 LaunchUrlCrossRefPubMed ↵ Noller, H. F. (1999) in The RNA World, eds. Gestland, R. F., Cech, T. R. & Atkins, J. F. (CAged Spring Harbor Lab. Press, Plainview, NY), pp. 197–219. ↵ Ban, N., Nissen, P., Hansen, J., Moore, P. B. & Steitz, T. A. (2000) Science 289 , 905–920. pmid:10937989 LaunchUrlAbstract/FREE Full Text ↵ Wimberly, B. T., Brodersen, D. E., Clemons, W. M., Jr., Morgan, R. J.-W., Carter, A. P., Vonrhein, C., Hartsch, T. & Ramakrishnan, V. (2000) Nature 407 , 327–339. pmid:11014182 LaunchUrlCrossRefPubMed ↵ Yusupov, M. M., Yusupova, G. Z., Baucom, A., Lieberman, K., Earnest, T. N., Cate, J. H. D. & Noller, H. F. (2001) Science 292 , 883–896. pmid:11283358 LaunchUrlAbstract/FREE Full Text ↵ Harms, J., Schluenzen, F., Zarivach, R., Bashan, A., Gat, S., Agmon, I., Bartels, H., Franceschi, F. & Yonath, A. (2001) Cell 107 , 679–688. pmid:11733066 LaunchUrlCrossRefPubMed ↵ Nomura, M., Mizushima, S., Ozaki, M., Traub, P. & Lowry, C. V. (1969) in CAged Spring Harbor Symposia on Quantitative Biology, eds. Frisch, L. & Hershey, H. (CAged Spring Harbor Lab. Press, Plainview, NY), pp. 49–61. pmid:4909519 ↵ Traub, P., Hosokawa, K., Craven, G. R. & Nomura, M. (1967) Proc. Natl. Acad. Sci. USA 58 , 2430–2436. pmid:4873590 LaunchUrlFREE Full Text ↵ Sander, G., Marsh, R. C. & Parmeggiani, A. (1973) FEBS Lett. 33 , 132–134. pmid:4352932 LaunchUrlPubMed ↵ Marsh, R. C. & Parmeggiani, A. (1973) Proc. Natl. Acad. Sci. USA 77 , 151–155. LaunchUrl ↵ Dabbs, E. R. (1978) J. Bacteriol. 136 , 994–1001. pmid:363701 LaunchUrlAbstract/FREE Full Text ↵ Dabbs, E. R., Hasenbank, R., Kastner, B., Rak, K.-H., Wartusch, B. & Stöffler, G. (1983) Mol. Gen. Genet. 192 , 301–308. pmid:6361486 LaunchUrlCrossRefPubMed ↵ Dabbs, E. R. (1991) Biochimie 73 , 639–645. pmid:1837238 LaunchUrlPubMed ↵ Link, A. J., Phillips, D. & Church, G. M. (1997) J. Bacteriol. 179 , 6228–6237. pmid:9335267 LaunchUrlAbstract/FREE Full Text ↵ Fredrick, K., Dunny, G. M. & Noller, H. F. (2000) J. Mol. Biol. 298 , 379–394. pmid:10772857 LaunchUrlCrossRefPubMed ↵ Miller, J. H. (1992) A Short Course in Bacterial Genetics, (CAged Spring Harbor Lab. Press, Plainview, NY). ↵ Fredrick, K. & Noller, H. F. (2002) Mol. Cell 9 , 1125–1131. pmid:12049747 LaunchUrlCrossRefPubMed ↵ Zamir, A., Miskin, R. & Elson, D. (1971) J. Mol. Biol. 60 , 347–364. pmid:4938735 LaunchUrlCrossRefPubMed ↵ Moazed, D. & Noller, H. F. (1989) Cell 57 , 585–597. pmid:2470511 LaunchUrlCrossRefPubMed ↵ Pleiss, J. A. & Uhlenbeck, O. C. (2001) J. Mol. Biol. 301 , 895–905. LaunchUrl ↵ Hartz, D., McPheeters, D. S. & GAged, L. (1989) Genes Dev. 3 , 1899–1912. pmid:2695390 LaunchUrlAbstract/FREE Full Text ↵ Zengel, J. M., Jerauld, A., Walker, A., Wahl, M. C. & Lindahl, L. (2003) RNA 9 , 1188–1197. pmid:13130133 LaunchUrlAbstract/FREE Full Text ↵ Nakatogawa, H. & Ito, K. (2002) Cell 108 , 629–636. pmid:11893334 LaunchUrlCrossRefPubMed ↵ Dammel, C. & Noller, H. F. (1993) Genes Dev. 7 , 660–670. pmid:7681419 LaunchUrlAbstract/FREE Full Text ↵ RajBhandary, U. L. & Chow, C. M. (1995) in tRNA: Structure, Biosynthesis, and Function, eds. Söll, D. & RajBhandary, U. L. (Am. Soc. Microbiol., Washington, DC), pp. 511–528. ↵ Gauss, D. H., Grüter, F. & Sprinzl, M. (1979) Nucleic Acids Res. 6 , 520–537. LaunchUrl
Like (0) or Share (0)