View source for 5kcr

{{Large structure}}
==Cryo-EM structure of the Escherichia coli 70S ribosome in complex with antibiotic Avilamycin C, mRNA and P-site tRNA at 3.6A resolution==
<StructureSection load='5kcr' size='340' side='right' caption='[[5kcr]], [[Resolution|resolution]] 3.60&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[5kcr]] is a 55 chain structure with sequence from [http://en.wikipedia.org/wiki/Ecoli Ecoli] and [http://en.wikipedia.org/wiki/Escherichia_coli_(strain_k12) Escherichia coli (strain k12)]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=5KCR OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=5KCR FirstGlance]. <br>
</td></tr><tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat"><scene name='pdbligand=6UQ:(2R,3S,4R,6S)-4-HYDROXY-6-{[(2R,3AR,4R,4R,5S,6S,6R,7AR)-4-HYDROXY-6-{[(2S,3R,4R,5S,6R)-3-HYDROXY-2-{[(2R,3S,4S,5S,6S)-4-HYDROXY-6-({(2R,3AS,3AR,6S,6R,7R,7R,7AR,7AR)-7-HYDROXY-7-[(1S)-1-HYDROXYETHYL]-6-METHYL-7-[(2-METHYLPROPANOYL)OXY]OCTAHYDRO-4H-2,4-SPIROBI[[1,3]DIOXOLO[4,5-C]PYRAN]-6-YL}OXY)-5-METHOXY-2-(METHOXYMETHYL)TETRAHYDRO-2H-PYRAN-3-YL]OXY}-5-METHOXY-6-METHYLTETRAHYDRO-2H-PYRAN-4-YL]OXY}-4,6,7A-TRIMETHYLOCTAHYDRO-4H-SPIRO[1,3-DIOXOLO[4,5-C]PYRAN-2,2-PYRAN]-5-YL]OXY}-2-METHYLTETRAHYDRO-2H-PYRAN-3-YL+3,5-DICHLORO-4-HYDROXY-2-METHOXY-6-METHYLBENZOATE+(NON-PREFERRED+NAME)'>6UQ</scene>, <scene name='pdbligand=ZN:ZINC+ION'>ZN</scene></td></tr>
<tr id='NonStdRes'><td class="sblockLbl"><b>[[Non-Standard_Residue|NonStd Res:]]</b></td><td class="sblockDat"><scene name='pdbligand=1MG:1N-METHYLGUANOSINE-5-MONOPHOSPHATE'>1MG</scene>, <scene name='pdbligand=2MA:2-METHYLADENOSINE-5-MONOPHOSPHATE'>2MA</scene>, <scene name='pdbligand=2MG:2N-METHYLGUANOSINE-5-MONOPHOSPHATE'>2MG</scene>, <scene name='pdbligand=5MC:5-METHYLCYTIDINE-5-MONOPHOSPHATE'>5MC</scene>, <scene name='pdbligand=5MU:5-METHYLURIDINE+5-MONOPHOSPHATE'>5MU</scene>, <scene name='pdbligand=6MZ:N6-METHYLADENOSINE-5-MONOPHOSPHATE'>6MZ</scene>, <scene name='pdbligand=G7M:N7-METHYL-GUANOSINE-5-MONOPHOSPHATE'>G7M</scene>, <scene name='pdbligand=H2U:5,6-DIHYDROURIDINE-5-MONOPHOSPHATE'>H2U</scene>, <scene name='pdbligand=MEQ:N5-METHYLGLUTAMINE'>MEQ</scene>, <scene name='pdbligand=OMC:O2-METHYLYCYTIDINE-5-MONOPHOSPHATE'>OMC</scene>, <scene name='pdbligand=OMG:O2-METHYLGUANOSINE-5-MONOPHOSPHATE'>OMG</scene>, <scene name='pdbligand=OMU:O2-METHYLURIDINE+5-MONOPHOSPHATE'>OMU</scene>, <scene name='pdbligand=PSU:PSEUDOURIDINE-5-MONOPHOSPHATE'>PSU</scene></td></tr>
<tr id='related'><td class="sblockLbl"><b>[[Related_structure|Related:]]</b></td><td class="sblockDat">[[5kcs|5kcs]]</td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=5kcr FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=5kcr OCA], [http://pdbe.org/5kcr PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=5kcr RCSB], [http://www.ebi.ac.uk/pdbsum/5kcr PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=5kcr ProSAT]</span></td></tr>
</table>
{{Large structure}}
== Function ==
[[http://www.uniprot.org/uniprot/RL23_ECOLI RL23_ECOLI]] One of the early assembly proteins, it binds 23S rRNA; is essential for growth. One of the proteins that surround the polypeptide exit tunnel on the outside of the subunit. Acts as the docking site for trigger factor (PubMed:12226666) for Ffh binding to the ribosome (SRP54, PubMed:12756233 and PubMed:12702815) and to nascent polypeptide chains (PubMed:12756233).[HAMAP-Rule:MF_01369] [[http://www.uniprot.org/uniprot/RL6_ECOLI RL6_ECOLI]] This protein binds directly to at least 2 domains of the 23S ribosomal RNA, thus is important in its secondary structure. It is located near the subunit interface in the base of the L7/L12 stalk, and near the tRNA binding site of the peptidyltransferase center.[HAMAP-Rule:MF_01365]  Gentamicin-resistant mutations in this protein affect translation fidelity.[HAMAP-Rule:MF_01365] [[http://www.uniprot.org/uniprot/RL29_ECOLI RL29_ECOLI]] Binds 23S rRNA. It is not essential for growth.[HAMAP-Rule:MF_00374]  One of the proteins that surrounds the polypeptide exit tunnel on the outside of the subunit. Contacts trigger factor (PubMed:12226666).[HAMAP-Rule:MF_00374] [[http://www.uniprot.org/uniprot/RL19_ECOLI RL19_ECOLI]] This protein is located at the 30S-50S ribosomal subunit interface. In the 70S ribosome (PubMed:12809609) it has been modeled to make two contacts with the 16S rRNA of the 30S subunit forming part of bridges B6 and B8. In the 3.5 A resolved structures (PubMed:16272117) L14 and L19 interact and together make contact with the 16S rRNA. The protein conformation is quite different between the 50S and 70S structures, which may be necessary for translocation.[HAMAP-Rule:MF_00402] [[http://www.uniprot.org/uniprot/RL20_ECOLI RL20_ECOLI]] One of the primary rRNA binding proteins, it binds close to the 5'-end of the 23S rRNA. It is important during the early stages of 50S assembly.[HAMAP-Rule:MF_00382] [[http://www.uniprot.org/uniprot/RL18_ECOLI RL18_ECOLI]] This is one of the proteins that mediates the attachment of the 5S rRNA subcomplex onto the large ribosomal subunit where it forms part of the central protuberance. Binds stably to 5S rRNA; increases binding abilities of L5 in a cooperative fashion; both proteins together confer 23S rRNA binding. The 5S rRNA and some of its associated proteins might help stabilize positioning of ribosome-bound tRNAs.<ref>PMID:353728</ref>  [[http://www.uniprot.org/uniprot/RS12_ECOLI RS12_ECOLI]] With S4 and S5 plays an important role in translational accuracy.[HAMAP-Rule:MF_00403_B]  Interacts with and stabilizes bases of the 16S rRNA that are involved in tRNA selection in the A site and with the mRNA backbone. Located at the interface of the 30S and 50S subunits, it traverses the body of the 30S subunit contacting proteins on the other side and probably holding the rRNA structure together. The combined cluster of proteins S8, S12 and S17 appears to hold together the shoulder and platform of the 30S subunit (By similarity).[HAMAP-Rule:MF_00403_B]  Cryo-EM studies suggest that S12 contacts the EF-Tu bound tRNA in the A-site during codon-recognition. This contact is most likely broken as the aminoacyl-tRNA moves into the peptidyl transferase center in the 50S subunit.[HAMAP-Rule:MF_00403_B] [[http://www.uniprot.org/uniprot/RS8_ECOLI RS8_ECOLI]] One of the primary rRNA binding proteins, it binds directly to 16S rRNA central domain where it helps coordinate assembly of the platform of the 30S subunit (By similarity).[HAMAP-Rule:MF_01302_B]  Protein S8 is a translational repressor protein, it controls the translation of the spc operon by binding to its mRNA.[HAMAP-Rule:MF_01302_B] [[http://www.uniprot.org/uniprot/RL22_ECOLI RL22_ECOLI]] This protein binds specifically to 23S rRNA; its binding is stimulated by other ribosomal proteins, e.g. L4, L17, and L20. It is important during the early stages of 50S assembly. It makes multiple contacts with different domains of the 23S rRNA in the assembled 50S subunit and ribosome.[HAMAP-Rule:MF_01331_B]  The globular domain of the protein is one of the proteins that surrounds the polypeptide exit tunnel on the outside of the subunit, while an extended beta-hairpin is found that penetrates into the center of the 70S ribosome where it lines the wall of the exit tunnel. Removal of most of this hairpin (residues 85-95) does not prevent its incorporation into 70S ribosomes. Two of the hairpin residues (91 and 93) seem to be involved in translation elongation arrest of the SecM protein, as their replacement by larger amino acids alleviates the arrest.[HAMAP-Rule:MF_01331_B] [[http://www.uniprot.org/uniprot/RL16_ECOLI RL16_ECOLI]] This protein binds directly to 23S ribosomal RNA and is located at the A site of the peptidyltransferase center. It contacts the A and P site tRNAs. It has an essential role in subunit assembly, which is not well understood.[HAMAP-Rule:MF_01342] [[http://www.uniprot.org/uniprot/RS17_ECOLI RS17_ECOLI]] One of the primary rRNA binding proteins, it binds specifically to the 5'-end of 16S ribosomal RNA. Also plays a role in translational accuracy; neamine-resistant ribosomes show reduced neamine-induced misreading in vitro.[HAMAP-Rule:MF_01345] [[http://www.uniprot.org/uniprot/RL11_ECOLI RL11_ECOLI]] This protein binds directly to 23S ribosomal RNA. Forms the L11 stalk, which is mobile in the ribosome, indicating its contribution to the activity of initiation, elongation and release factors.[HAMAP-Rule:MF_00736_B] [[http://www.uniprot.org/uniprot/RS3_ECOLI RS3_ECOLI]] Binds the lower part of the 30S subunit head. Binds mRNA in the 70S ribosome, positioning it for translation (By similarity).<ref>PMID:15652481</ref>   Plays a role in mRNA unwinding by the ribosome, possibly by forming part of a processivity clamp.<ref>PMID:15652481</ref>  [[http://www.uniprot.org/uniprot/RL13_ECOLI RL13_ECOLI]] This protein is one of the early assembly proteins of the 50S ribosomal subunit, although it is not seen to bind rRNA by itself. It is important during the early stages of 50S assembly.[HAMAP-Rule:MF_01366] [[http://www.uniprot.org/uniprot/RS16_ECOLI RS16_ECOLI]] In addition to being a ribosomal protein, S16 also has a cation-dependent endonuclease activity.<ref>PMID:8730873</ref>   In-frame fusions with the ribosome maturation factor rimM suppress mutations in the latter (probably due to increased rimM expression) and are found in translationally active 70S ribosomes.<ref>PMID:8730873</ref>  [[http://www.uniprot.org/uniprot/RS10_ECOLI RS10_ECOLI]] Involved in the binding of tRNA to the ribosomes.[HAMAP-Rule:MF_00508] [[http://www.uniprot.org/uniprot/RL24_ECOLI RL24_ECOLI]] One of two assembly initiator proteins, it binds directly to the 5'-end of the 23S rRNA, where it nucleates assembly of the 50S subunit. It is not thought to be involved in the functions of the mature 50S subunit in vitro.<ref>PMID:357435</ref>   One of the proteins that surrounds the polypeptide exit tunnel on the outside of the subunit.<ref>PMID:357435</ref>  [[http://www.uniprot.org/uniprot/RS14_ECOLI RS14_ECOLI]] Binds 16S rRNA, required for the assembly of 30S particles and may also be responsible for determining the conformation of the 16S rRNA at the A site.[HAMAP-Rule:MF_00537] [[http://www.uniprot.org/uniprot/RL15_ECOLI RL15_ECOLI]] This protein binds the 5S rRNA. It is required for the late stages of subunit assembly, and is essential for 5S rRNA assembly onto the ribosome.[HAMAP-Rule:MF_01341_B] [[http://www.uniprot.org/uniprot/RL25_ECOLI RL25_ECOLI]] This is one of the proteins that binds to the 5S RNA in the ribosome where it forms part of the central protuberance. Binds to the 5S rRNA independently of L5 and L18. Not required for binding of the 5S rRNA/L5/L18 subcomplex to 23S rRNA.[HAMAP-Rule:MF_01336] [[http://www.uniprot.org/uniprot/RL5_ECOLI RL5_ECOLI]] This is 1 of the proteins that binds and probably mediates the attachment of the 5S RNA into the large ribosomal subunit, where it forms part of the central protuberance. Its 5S rRNA binding is significantly enhanced in the presence of L18.[HAMAP-Rule:MF_01333_B]  In the 70S ribosome in the initiation state (PubMed:12809609) was modeled to contact protein S13 of the 30S subunit (bridge B1b), connecting the 2 subunits; the protein-protein contacts between S13 and L5 in B1b change in the model with bound EF-G implicating this bridge in subunit movement (PubMed:12809609 and PubMed:18723842). In the two 3.5 A resolved ribosome structures (PubMed:16272117) the contacts between L5, S13 and S19 are different, confirming the dynamic nature of this interaction.[HAMAP-Rule:MF_01333_B]  Contacts the P site tRNA; the 5S rRNA and some of its associated proteins might help stabilize positioning of ribosome-bound tRNAs.[HAMAP-Rule:MF_01333_B] [[http://www.uniprot.org/uniprot/RS18_ECOLI RS18_ECOLI]] Binds as a heterodimer with protein S6 to the central domain of the 16S rRNA, where it helps stabilize the platform of the 30S subunit.[HAMAP-Rule:MF_00270] [[http://www.uniprot.org/uniprot/RS7_ECOLI RS7_ECOLI]] One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it nucleates assembly of the head domain of the 30S subunit. Is located at the subunit interface close to the decoding center, where it has been shown to contact mRNA. Has been shown to contact tRNA in both the P and E sites; it probably blocks exit of the E site tRNA.<ref>PMID:2461734</ref>   Protein S7 is also a translational repressor protein; it regulates the expression of the str operon members to different degrees by binding to its mRNA.<ref>PMID:2461734</ref>  [[http://www.uniprot.org/uniprot/RS4_ECOLI RS4_ECOLI]] One of two assembly initiator proteins for the 30S subunit, it binds directly to 16S rRNA where it nucleates assembly of the body of the 30S subunit.<ref>PMID:2461734</ref> <ref>PMID:11447122</ref> <ref>PMID:15652481</ref>   With S5 and S12 plays an important role in translational accuracy; many suppressors of streptomycin-dependent mutants of protein S12 are found in this protein, some but not all of which decrease translational accuracy (ram, ribosomal ambiguity mutations).<ref>PMID:2461734</ref> <ref>PMID:11447122</ref> <ref>PMID:15652481</ref>   Plays a role in mRNA unwinding by the ribosome, possibly by forming part of a processivity clamp.<ref>PMID:2461734</ref> <ref>PMID:11447122</ref> <ref>PMID:15652481</ref>   Protein S4 is also a translational repressor protein, it controls the translation of the alpha-operon (which codes for S13, S11, S4, RNA polymerase alpha subunit, and L17) by binding to its mRNA.<ref>PMID:2461734</ref> <ref>PMID:11447122</ref> <ref>PMID:15652481</ref>   Also functions as a rho-dependent antiterminator of rRNA transcription, increasing the synthesis of rRNA under conditions of excess protein, allowing a more rapid return to homeostasis. Binds directly to RNA polymerase.<ref>PMID:2461734</ref> <ref>PMID:11447122</ref> <ref>PMID:15652481</ref>  [[http://www.uniprot.org/uniprot/RL2_ECOLI RL2_ECOLI]] One of the primary rRNA binding proteins. Located near the base of the L1 stalk, it is probably also mobile. Required for association of the 30S and 50S subunits to form the 70S ribosome, for tRNA binding and peptide bond formation. It has been suggested to have peptidyltransferase activity; this is highly controversial.[HAMAP-Rule:MF_01320_B]  In the E.coli 70S ribosome in the initiation state it has been modeled to make several contacts with the 16S rRNA (forming bridge B7b, PubMed:12809609); these contacts are broken in the model with bound EF-G.[HAMAP-Rule:MF_01320_B] [[http://www.uniprot.org/uniprot/RS19_ECOLI RS19_ECOLI]] In the E.coli 70S ribosome in the initiation state (PubMed:12809609) it has been modeled to contact the 23S rRNA of the 50S subunit forming part of bridge B1a; this bridge is broken in the model with bound EF-G. The 23S rRNA contact site in bridge B1a is modeled to differ in different ribosomal states (PubMed:12859903), contacting alternately S13 or S19. In the 3.5 angstroms resolved ribosome structures (PubMed:16272117) the contacts between L5, S13 and S19 bridge B1b are different, confirming the dynamic nature of this interaction. Bridge B1a is not visible in the crystallized ribosomes due to 23S rRNA disorder.[HAMAP-Rule:MF_00531]  Protein S19 forms a complex with S13 that binds strongly to the 16S ribosomal RNA. Contacts the A site tRNA.[HAMAP-Rule:MF_00531] [[http://www.uniprot.org/uniprot/RL10_ECOLI RL10_ECOLI]] Protein L10 is also a translational repressor protein. It controls the translation of the rplJL-rpoBC operon by binding to its mRNA.[HAMAP-Rule:MF_00362] [[http://www.uniprot.org/uniprot/RS9_ECOLI RS9_ECOLI]] The C-terminal tail plays a role in the affinity of the 30S P site for different tRNAs. Mutations that decrease this affinity are suppressed in the 70S ribosome.<ref>PMID:15308780</ref>  [[http://www.uniprot.org/uniprot/RL14_ECOLI RL14_ECOLI]] This protein binds directly to 23S ribosomal RNA. In the E.coli 70S ribosome (PubMed:12809609) it has been modeled to make two contacts with the 16S rRNA of the 30S subunit, forming part of bridges B5 and B8, connecting the 2 subunits. Although the protein undergoes significant rotation during the transition from an initiation to and EF-G bound state, the bridges remain stable. In the 3.5 A resolved structures (PubMed:16272117) L14 and L19 interact and together make contact with the 16S rRNA in bridges B5 and B8.<ref>PMID:22829778</ref>   Can also interact with RsfA, in this case bridge B8 probably cannot form, and the 30S and 50S ribosomal subunits do not associate, which represses translation.<ref>PMID:22829778</ref>  [[http://www.uniprot.org/uniprot/RS15_ECOLI RS15_ECOLI]] One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it helps nucleate assembly of the platform of the 30S subunit by binding and bridging several RNA helices of the 16S rRNA.[HAMAP-Rule:MF_01343]  In the E.coli 70S ribosome it has been modeled (PubMed:12809609) to contact the 23S rRNA of the 50S subunit forming part of bridge B4. In the two 3.5 A resolved ribosome structures (PubMed:16272117) there are minor differences between side-chain conformations.[HAMAP-Rule:MF_01343] [[http://www.uniprot.org/uniprot/RL17_ECOLI RL17_ECOLI]] Requires L15 for assembly into the 50S subunit.[HAMAP-Rule:MF_01368] [[http://www.uniprot.org/uniprot/RS20_ECOLI RS20_ECOLI]] Binds directly to 16S ribosomal RNA.[HAMAP-Rule:MF_00500] [[http://www.uniprot.org/uniprot/RS6_ECOLI RS6_ECOLI]] Binds together with S18 to 16S ribosomal RNA.[HAMAP-Rule:MF_00360] [[http://www.uniprot.org/uniprot/RL9_ECOLI RL9_ECOLI]] One of the primary rRNA binding proteins, it binds very close to the 3' end of the 23S rRNA.[HAMAP-Rule:MF_00503] [[http://www.uniprot.org/uniprot/RL3_ECOLI RL3_ECOLI]] One of two assembly inititator proteins, it binds directly near the 3'-end of the 23S rRNA, where it nucleates assembly of the 50S subunit.[HAMAP-Rule:MF_01325_B] [[http://www.uniprot.org/uniprot/RS13_ECOLI RS13_ECOLI]] Located at the top of the head of the 30S subunit, it contacts several helices of the 16S rRNA.<ref>PMID:15308780</ref>   In the E.coli 70S ribosome in the initiation state (PubMed:12809609) was modeled to contact the 23S rRNA (bridge B1a) and protein L5 of the 50S subunit (bridge B1b), connecting the 2 subunits; bridge B1a is broken in the model with bound EF-G, while the protein-protein contacts between S13 and L5 in B1b change (PubMed:12809609). The 23S rRNA contact site in bridge B1a is modeled to differ in different ribosomal states (PubMed:16272117), contacting alternately S13 or S19. In the two 3.5 angstroms resolved ribosome structures (PubMed:12859903) the contacts between L5, S13 and S19 bridge B1b are different, confirming the dynamic nature of this interaction. Bridge B1a is not visible in the crystallized ribosomes due to 23S rRNA disorder.<ref>PMID:15308780</ref>   Contacts the tRNAs in the A and P sites.<ref>PMID:15308780</ref>   The C-terminal tail plays a role in the affinity of the 30S P site for different tRNAs.<ref>PMID:15308780</ref>  [[http://www.uniprot.org/uniprot/RS5_ECOLI RS5_ECOLI]] With S4 and S12 plays an important role in translational accuracy. Many suppressors of streptomycin-dependent mutants of protein S12 are found in this protein, some but not all of which decrease translational accuracy (ram, ribosomal ambiguity mutations).<ref>PMID:15652481</ref>   Located at the back of the 30S subunit body where it stabilizes the conformation of the head with respect to the body.<ref>PMID:15652481</ref>   The physical location of this protein suggests it may also play a role in mRNA unwinding by the ribosome, possibly by forming part of a processivity clamp.<ref>PMID:15652481</ref>  [[http://www.uniprot.org/uniprot/RS11_ECOLI RS11_ECOLI]] Located on the platform of the 30S subunit, it bridges several disparate RNA helices of the 16S rRNA. Forms part of the Shine-Dalgarno cleft in the 70S ribosome (By similarity).[HAMAP-Rule:MF_01310] [[http://www.uniprot.org/uniprot/RL21_ECOLI RL21_ECOLI]] This protein binds to 23S rRNA in the presence of protein L20.[HAMAP-Rule:MF_01363] [[http://www.uniprot.org/uniprot/RL4_ECOLI RL4_ECOLI]] One of the primary rRNA binding proteins, this protein initially binds near the 5'-end of the 23S rRNA. It is important during the early stages of 50S assembly. It makes multiple contacts with different domains of the 23S rRNA in the assembled 50S subunit and ribosome.<ref>PMID:2442760</ref>   Protein L4 is a both a transcriptional repressor and a translational repressor protein; these two functions are independent of each other. It regulates transcription of the S10 operon (to which L4 belongs) by causing premature termination of transcription within the S10 leader; termination absolutely requires the NusA protein. L4 controls the translation of the S10 operon by binding to its mRNA. The regions of L4 that control regulation (residues 131-210) are different from those required for ribosome assembly (residues 89-103).<ref>PMID:2442760</ref>   Forms part of the polypeptide exit tunnel.<ref>PMID:2442760</ref>   Can regulate expression from Citrobacter freundii, Haemophilus influenzae, Morganella morganii, Salmonella typhimurium, Serratia marcescens, Vibrio cholerae and Yersinia enterocolitica (but not Pseudomonas aeruginosa) S10 leaders in vitro.<ref>PMID:2442760</ref>  
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The ribosome is one of the major targets for therapeutic antibiotics; however, the rise in multidrug resistance is a growing threat to the utility of our current arsenal. The orthosomycin antibiotics evernimicin (EVN) and avilamycin (AVI) target the ribosome and do not display cross-resistance with any other classes of antibiotics, suggesting that they bind to a unique site on the ribosome and may therefore represent an avenue for development of new antimicrobial agents. Here we present cryo-EM structures of EVN and AVI in complex with the Escherichia coli ribosome at 3.6- to 3.9-A resolution. The structures reveal that EVN and AVI bind to a single site on the large subunit that is distinct from other known antibiotic binding sites on the ribosome. Both antibiotics adopt an extended conformation spanning the minor grooves of helices 89 and 91 of the 23S rRNA and interacting with arginine residues of ribosomal protein L16. This binding site overlaps with the elbow region of A-site bound tRNA. Consistent with this finding, single-molecule FRET (smFRET) experiments show that both antibiotics interfere with late steps in the accommodation process, wherein aminoacyl-tRNA enters the peptidyltransferase center of the large ribosomal subunit. These data provide a structural and mechanistic rationale for how these antibiotics inhibit the elongation phase of protein synthesis.

Structures of the orthosomycin antibiotics avilamycin and evernimicin in complex with the bacterial 70S ribosome.,Arenz S, Juette MF, Graf M, Nguyen F, Huter P, Polikanov YS, Blanchard SC, Wilson DN Proc Natl Acad Sci U S A. 2016 Jul 5;113(27):7527-32. doi:, 10.1073/pnas.1604790113. Epub 2016 Jun 21. PMID:27330110<ref>PMID:27330110</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 5kcr" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Ecoli]]
[[Category: Arenz, S]]
[[Category: Blanchard, S C]]
[[Category: Graf, M]]
[[Category: Huter, P]]
[[Category: Juette, M F]]
[[Category: Nguyen, F]]
[[Category: Polikanov, Y S]]
[[Category: Wilson, D N]]
[[Category: Antibiotic]]
[[Category: Antimicrobial]]
[[Category: Avilamycin]]
[[Category: Cryo-em]]
[[Category: Evernimycin]]
[[Category: L16]]
[[Category: Resistance]]
[[Category: Ribosome]]
[[Category: Rrna]]
[[Category: Smfret]]
[[Category: Translation]]