6q95
Structure of tmRNA SmpB bound in A site of T. thermophilus 70S ribosome
Structural highlights
Function[RL34_THET8] Found on the solvent side of the large subunit.[HAMAP-Rule:MF_00391] [RSHX_THET8] Binds at the top of the head of the 30S subunit. It stabilizes a number of different RNA elements and thus is important for subunit structure. [RS7_THET8] One of the primary rRNA binding proteins, it binds directly to 3'-end of the 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. Binds mRNA and the E site tRNA blocking its exit path in the ribosome. This blockage implies that this section of the ribosome must be able to move to release the deacetylated tRNA.[HAMAP-Rule:MF_00480_B] [RS2_THET8] Spans the head-body hinge region of the 30S subunit. Is loosely associated with the 30S subunit.[HAMAP-Rule:MF_00291_B] [RS17_THET8] One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it helps nucleate assembly of the platform and body of the 30S subunit by bringing together and stabilizing interactions between several different RNA helices. The combined cluster of proteins S8, S12 and S17 appears to hold together the shoulder and platform of the 30S subunit.[HAMAP-Rule:MF_01345] Deletion of the protein leads to an increased generation time and a temperature-sensitive phenotype.[HAMAP-Rule:MF_01345] [RS18_THET8] Located on the back of the platform of the 30S subunit where it stabilizes the close packing of several RNA helices of the 16S rRNA. Forms part of the Shine-Dalgarno cleft in the 70S ribosome, where it probably interacts with the Shine-Dalgarno helix.[HAMAP-Rule:MF_00270] [RL32_THET8] Found on the solvent side of the large subunit.[HAMAP-Rule:MF_00340] [RS16_THET8] Binds to the lower part of the body of the 30S subunit, where it stabilizes two of its domains.[HAMAP-Rule:MF_00385] [RL14_THET8] This protein binds directly to 23S ribosomal RNA (By similarity).[HAMAP-Rule:MF_01367] Contacts the 16S rRNA of the 30S subunit in two different positions helping to form bridges B5 and B8.[HAMAP-Rule:MF_01367] [RL25_THET8] This is one of 3 proteins that mediate the attachment of the 5S rRNA onto the large ribosomal subunit.[HAMAP-Rule:MF_01334] [RL29_THET8] One of the proteins that surrounds the polypeptide exit tunnel on the outside of the subunit.[HAMAP-Rule:MF_00374] [RL27_THET8] Found on the solvent side of the large subunit.[HAMAP-Rule:MF_00539] [RL5_THET8] 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. In the 70S ribosome it contacts protein S13 of the 30S subunit (forming bridge B1b) connecting the head of the 30S subunit to the top of the 50S subunit. The bridge itself contacts the P site tRNA and is implicated in movement during ribosome translocation. Also contacts the P site tRNA independently of the intersubunit bridge; the 5S rRNA and some of its associated proteins might help stabilize positioning of ribosome-bound tRNAs.[HAMAP-Rule:MF_01333_B] [RS14Z_THET8] Required for the assembly of 30S particles and may also be responsible for determining the conformation of the 16S rRNA at the A site (By similarity). Binds 16S rRNA in center of the 30S subunit head.[HAMAP-Rule:MF_01364_B] [RS20_THET8] One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it nucleates assembly of the bottom of the body of the 30S subunit, by binding to several RNA helices of the 16S rRNA.[HAMAP-Rule:MF_00500] [RL19_THET8] Contacts the 16S rRNA of the 30S subunit (part of bridge B6), connecting the 2 subunits.[HAMAP-Rule:MF_00402] [RS10_THET8] Part of the top of the 30S subunit head.[HAMAP-Rule:MF_00508] [RL33_THET8] Found on the solvent side of the large subunit.[HAMAP-Rule:MF_00294] Contacts the E site tRNA.[HAMAP-Rule:MF_00294] [RS11_THET8] Located on the upper part of the platform of the 30S subunit, where it bridges several disparate RNA helices of the 16S rRNA. Forms part of the Shine-Dalgarno cleft in the 70S ribosome, where it interacts both with the Shine-Dalgarno helix and mRNA.[HAMAP-Rule:MF_01310] [RL23_THET8] One of the early assembly proteins (By similarity) it binds 23S rRNA. One of the proteins that surrounds the polypeptide exit tunnel on the outside of the ribosome. Forms the main docking site for trigger factor binding to the ribosome (By similarity).[HAMAP-Rule:MF_01369] [RL18_THET8] This is one of the proteins that binds and mediates the attachment of the 5S RNA into the large ribosomal subunit, where it forms part of the central protuberance.[HAMAP-Rule:MF_01337_B] [RL9_THET8] Binds to the 23S rRNA. Extends more that 50 Angstroms beyond the surface of the 70S ribosome.[HAMAP-Rule:MF_00503] [RL16_THET8] This protein binds directly to 23S rRNA. Interacts with the A site tRNA.[HAMAP-Rule:MF_01342] [RS13_THET8] Located at the top of the head of the 30S subunit, it contacts several helices of the 16S rRNA. In the 70S ribosome structure it contacts the 23S rRNA (bridge B1a) and protein L5 of the 50S subunit (bridge B1b), connecting the top of the two subunits; these bridges are in contact with the A site and P site tRNAs respectively and are implicated in movement during ribosome translocation. Separately contacts the tRNAs in the A and P sites.[HAMAP-Rule:MF_01315] [RL31_THET8] Binds the 23S rRNA (By similarity).[HAMAP-Rule:MF_00501] [RS6_THET8] Located on the outer edge of the platform on the body of the 30S subunit.[HAMAP-Rule:MF_00360] [RL20_THET8] Binds directly to 23S ribosomal RNA and is necessary for the in vitro assembly process of the 50S ribosomal subunit. It is not involved in the protein synthesizing functions of that subunit (By similarity).[HAMAP-Rule:MF_00382] [RL4_THET8] 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 (By similarity).[HAMAP-Rule:MF_01328_B] Forms part of the polypeptide exit tunnel (By similarity).[HAMAP-Rule:MF_01328_B] This protein can be incorporated into E.coli ribosomes in vivo, which resulted in decreased peptidyltransferase (Ptase) activity of the hybrid ribosomes. The hybrid 50S subunits associate less well with 30S subunits to form the ribosome.[HAMAP-Rule:MF_01328_B] [RS3_THET8] Binds the lower part of the 30S subunit head. Binds mRNA in the 70S ribosome, positioning it for translation.[HAMAP-Rule:MF_01309_B] [RL1_THET8] Directly binds to 23S rRNA. Forms what is known as the L1 stalk, which protrudes beyond the 70S ribosome surface. The stalk is preferentially stabilized in 70S versus 50S crystals. Interacts with the E site tRNA, blocking the exit path. This blockage implies that this section of the ribosome must be able to move to release the deacetylated tRNA.[HAMAP-Rule:MF_01318_B] Protein L1 is also a translational repressor protein, it controls the translation of the L11 operon by binding to its mRNA (By similarity).[HAMAP-Rule:MF_01318_B] [RS9_THET8] Part of the top of the head of the 30S subunit. The C-terminal region penetrates the head emerging in the P-site where it contacts tRNA.[HAMAP-Rule:MF_00532_B] [RL21_THET8] This protein binds to 23S rRNA in the presence of protein L20 (By similarity). Found on the solvent side of the large subunit.[HAMAP-Rule:MF_01363] [RL6_THET8] This protein binds to the 23S rRNA, and 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] [RS12_THET8] With S4 and S5 plays an important role in translational accuracy (By similarity).[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.[HAMAP-Rule:MF_00403_B] [RS15_THET8] 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 (By similarity).[HAMAP-Rule:MF_01343] Forms an intersubunit bridge (bridge B4) with the 23S rRNA of the 50S subunit in the ribosome.[HAMAP-Rule:MF_01343] [RS8_THET8] 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 central domain. The combined cluster of proteins S8, S12 and S17 appears to hold together the shoulder and platform of the 30S subunit.[HAMAP-Rule:MF_01302_B] [RL22_THET8] 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 (By similarity).[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. This extension seems to form part of the wall of the exit tunnel.[HAMAP-Rule:MF_01331_B] [RL3_THET8] One of the primary rRNA binding proteins, it binds directly near the 3'-end of the 23S rRNA, where it nucleates assembly of the 50S subunit (By similarity).[HAMAP-Rule:MF_01325_B] [RS4_THET8] One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it helps nucleate assembly of the body and platform of the 30S subunit. Binds mRNA in the 70S ribosome, positioning it for translation.[HAMAP-Rule:MF_01306_B] [SSRP_THET8] Binds specifically to the SsrA RNA (tmRNA) and is required for stable association of SsrA with ribosomes (By similarity). [RL15_THET8] Binds to the 23S rRNA (By similarity).[HAMAP-Rule:MF_01341_B] [RL2_THET8] One of the primary rRNA binding proteins. 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 somewhat controversial (By similarity). Makes several contacts with the 16S rRNA (forming bridge B7b) in the 70S ribosome.[HAMAP-Rule:MF_01320_B] [RL13_THET8] 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 (By similarity).[HAMAP-Rule:MF_01366] [RS19_THET8] Located at the top of the head of the 30S subunit, extending towards the 50S subunit, which it may contact in the 70S complex. Contacts several RNA helices of the 16S rRNA.[HAMAP-Rule:MF_00531] [RL24_THET8] 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 (By similarity).[HAMAP-Rule:MF_01326_B] One of the proteins that surrounds the polypeptide exit tunnel on the outside of the subunit.[HAMAP-Rule:MF_01326_B] [RS5_THET8] With S4 and S12 plays an important role in translational accuracy (By similarity).[HAMAP-Rule:MF_01307_B] Located at the back of the 30S subunit body where it stabilizes the conformation of the head with respect to the body. Binds mRNA in the 70S ribosome, positioning it for translation.[HAMAP-Rule:MF_01307_B] Publication Abstract from PubMedDuring trans-translation, transfer-messenger RNA (tmRNA) and small protein B (SmpB) together rescue ribosomes stalled on a truncated mRNA and tag the nascent polypeptide for degradation. We used cryo-electron microscopy to determine the structures of three key states of the tmRNA-SmpB-ribosome complex during trans translation at resolutions of 3.7 to 4.4 angstroms. The results show how tmRNA and SmpB act specifically on stalled ribosomes and how the circularized complex moves through the ribosome, enabling translation to switch from the old defective message to the reading frame on tmRNA. How a circularized tmRNA moves through the ribosome.,Rae CD, Gordiyenko Y, Ramakrishnan V Science. 2019 Feb 15;363(6428):740-744. doi: 10.1126/science.aav9370. PMID:30765567[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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