4a2i
From Proteopedia
Cryo-electron Microscopy Structure of the 30S Subunit in Complex with the YjeQ Biogenesis Factor
Structural highlights
Function[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] [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.[1] 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.[2] [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] [RSGA_SALTY] May play a role in 30S ribosomal subunit biogenesis. Unusual circulary permuted GTPase that catalyzes rapid hydrolysis of GTP with a slow catalytic turnover (By similarity).[HAMAP-Rule:MF_01820] [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] [RS13_ECOLI] Located at the top of the head of the 30S subunit, it contacts several helices of the 16S rRNA.[3] 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.[4] Contacts the tRNAs in the A and P sites.[5] The C-terminal tail plays a role in the affinity of the 30S P site for different tRNAs.[6] [RS16_ECOLI] In addition to being a ribosomal protein, S16 also has a cation-dependent endonuclease activity.[7] 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.[8] [RS6_ECOLI] Binds together with S18 to 16S ribosomal RNA.[HAMAP-Rule:MF_00360] [RS3_ECOLI] Binds the lower part of the 30S subunit head. Binds mRNA in the 70S ribosome, positioning it for translation (By similarity).[9] Plays a role in mRNA unwinding by the ribosome, possibly by forming part of a processivity clamp.[10] [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.[11] [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] [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] [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] [RS20_ECOLI] Binds directly to 16S ribosomal RNA.[HAMAP-Rule:MF_00500] [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] [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.[12] [13] [14] 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).[15] [16] [17] Plays a role in mRNA unwinding by the ribosome, possibly by forming part of a processivity clamp.[18] [19] [20] 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.[21] [22] [23] 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.[24] [25] [26] [RS10_ECOLI] Involved in the binding of tRNA to the ribosomes.[HAMAP-Rule:MF_00508] [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] [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).[27] Located at the back of the 30S subunit body where it stabilizes the conformation of the head with respect to the body.[28] 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.[29] Publication Abstract from PubMedYjeQ is a protein broadly conserved in bacteria containing an N-terminal oligonucleotide/oligosaccharide fold (OB-fold) domain, a central GTPase domain, and a C-terminal zinc-finger domain. YjeQ binds tightly and stoichiometrically to the 30S subunit, which stimulates its GTPase activity by 160-fold. Despite growing evidence for the involvement of the YjeQ protein in bacterial 30S subunit assembly, the specific function and mechanism of this protein remain unclear. Here, we report the costructure of YjeQ with the 30S subunit obtained by cryo-electron microscopy. The costructure revealed that YjeQ interacts simultaneously with helix 44, the head and the platform of the 30S subunit. This binding location of YjeQ in the 30S subunit suggests a chaperone role in processing of the 3' end of the rRNA as well as in mediating the correct orientation of the main domains of the 30S subunit. In addition, the YjeQ binding site partially overlaps with the interaction site of initiation factors 2 and 3, and upon binding, YjeQ covers three inter-subunit bridges that are important for the association of the 30S and 50S subunits. Hence, our structure suggests that YjeQ may assist in ribosome maturation by preventing premature formation of the translation initiation complex and association with the 50S subunit. Together, these results support a role for YjeQ in the late stages of 30S maturation. Cryo-electron microscopy structure of the 30S subunit in complex with the YjeQ biogenesis factor.,Jomaa A, Stewart G, Mears JA, Kireeva I, Brown ED, Ortega J RNA. 2011 Nov;17(11):2026-38. Epub 2011 Sep 29. PMID:21960487[30] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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