6o7k
30S initiation complex
Structural highlights
Function[S1D5F0_ECOLX] 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, probably blocks exit of the E-site tRNA.[HAMAP-Rule:MF_00480] [V6FZ95_ECOLX] 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][RuleBase:RU003623] With S4 and S5 plays an important role in translational accuracy.[HAMAP-Rule:MF_00403][RuleBase:RU003623] [A0A376HTV6_ECOLX] Binds the lower part of the 30S subunit head. Binds mRNA in the 70S ribosome, positioning it for translation.[HAMAP-Rule:MF_01309] [A0A069XYI1_ECOLX] One of the essential components for the initiation of protein synthesis. Protects formylmethionyl-tRNA from spontaneous hydrolysis and promotes its binding to the 30S ribosomal subunits. Also involved in the hydrolysis of GTP during the formation of the 70S ribosomal complex.[HAMAP-Rule:MF_00100][RuleBase:RU000644][SAAS:SAAS00362971] [D8A1L7_ECOMS] 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.[HAMAP-Rule:MF_01302] [L3PZ69_ECOLX] One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it nucleates assembly of the body of the 30S subunit.[HAMAP-Rule:MF_01306] With S5 and S12 plays an important role in translational accuracy.[HAMAP-Rule:MF_01306] [F4SQ43_ECOLX] Protein S19 forms a complex with S13 that binds strongly to the 16S ribosomal RNA.[HAMAP-Rule:MF_00531] [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] [A0A090BZT4_ECOLX] 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] [L3BXG0_ECOLX] 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] [S1CG62_ECOLX] Binds together with S18 to 16S ribosomal RNA.[HAMAP-Rule:MF_00360][SAAS:SAAS00348112] [T6N332_ECOLX] Binds directly to 16S ribosomal RNA.[HAMAP-Rule:MF_00500] [A0A1X3KX08_ECOLX] Located at the top of the head of the 30S subunit, it contacts several helices of the 16S rRNA. In the 70S ribosome it contacts the 23S rRNA (bridge B1a) and protein L5 of the 50S subunit (bridge B1b), connecting the 2 subunits; these bridges are implicated in subunit movement. Contacts the tRNAs in the A and P-sites.[HAMAP-Rule:MF_01315] [A0A080IK26_ECOLX] One of the primary rRNA binding proteins, it binds specifically to the 5'-end of 16S ribosomal RNA.[HAMAP-Rule:MF_01345] [B6I217_ECOSE] Located at the back of the 30S subunit body where it stabilizes the conformation of the head with respect to the body.[HAMAP-Rule:MF_01307][SAAS:SAAS00085417] With S4 and S12 plays an important role in translational accuracy.[HAMAP-Rule:MF_01307][SAAS:SAAS00085429] [D7XN21_ECOLX] Forms an intersubunit bridge (bridge B4) with the 23S rRNA of the 50S subunit in the ribosome.[HAMAP-Rule:MF_01343] 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][RuleBase:RU004524] [D7X302_ECOLX] Involved in the binding of tRNA to the ribosomes.[HAMAP-Rule:MF_00508] Publication Abstract from PubMedBacterial translation initiation entails the tightly regulated joining of the 50S ribosomal subunit to an initiator transfer RNA (fMet-tRNA(fMet))-containing 30S ribosomal initiation complex (IC) to form a 70S IC that subsequently matures into a 70S elongation-competent complex (70S EC). Rapid and accurate 70S IC formation is promoted by 30S IC-bound initiation factors (IFs), which must dissociate before the resulting 70S EC can begin translation elongation(1). Although comparison of 30S(2-5) and 70S(4,6-8) IC structures have revealed that the ribosome, IFs, and fMet-tRNA(fMet) can acquire different conformations in these complexes, the timing of conformational changes during 70S IC formation, structures of any intermediates formed during these rearrangements, and contributions that these dynamics might make to the mechanism and regulation of initiation remain unknown. Moreover, the absence of a 70S EC structure obtained directly from a 70S IC formed via an IF-catalysed initiation reaction has precluded an understanding of ribosome, IF, and fMet-tRNA(fMet) rearrangements that occur upon maturation of a 70S IC into a 70S EC. Using time-resolved cryogenic electron microscopy (TR cryo-EM)(9), we report the first, near-atomic-resolution view of how a time-ordered series of conformational changes drive and regulate subunit joining, IF dissociation, and fMet-tRNA(fMet) positioning during 70S EC formation. Our results demonstrate the power of TR cryo-EM to determine how a time-ordered series of conformational changes contribute to the mechanism and regulation of one of the most fundamental processes in biology. Late steps in bacterial translation initiation visualized using time-resolved cryo-EM.,Kaledhonkar S, Fu Z, Caban K, Li W, Chen B, Sun M, Gonzalez RL Jr, Frank J Nature. 2019 May 20. pii: 10.1038/s41586-019-1249-5. doi:, 10.1038/s41586-019-1249-5. PMID:31108498[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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