5x8p
From Proteopedia
Structure of the 70S chloroplast ribosome from spinach
Structural highlights
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Function[RK19_SPIOL] Located at the 30S-50S ribosomal subunit interface and binds directly to 23S ribosomal RNA (By similarity).[:] [RK24_SPIOL] 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). Located at the polypeptide exit tunnel on the outside of the subunit. [RK14_SPIOL] Binds to 23S rRNA (By similarity). [RRP2_SPIOL] May have a role in the recruitment of stored chloroplast mRNAs for active protein synthesis.[1] [RK23_SPIOL] Binds to 23S rRNA (By similarity). Located at the polypeptide exit tunnel on the outside of the subunit. [RK22_SPIOL] This protein binds specifically to 23S rRNA (By similarity). The globular domain of the protein is located near the polypeptide exit tunnel on the outside of the subunit, while an extended beta-hairpin is found that lines the wall of the exit tunnel in the center of the 70S ribosome (By similarity). Binds an erythromycin derivative added to the 50S subunit. [RR5_SPIOL] Binds directly to 16S ribosomal RNA. Involved in spectinomycin and neamine resistance and streptomycin independence.[:] [RK4_SPIOL] Probably binds the 23S rRNA (By similarity). This protein (expressed without the transit peptide) is able to provoke transcription termination from the spinach chloroplast rDNA operon and the E.coli S10 operon in vitro. [RRP3_SPIOL] One of the plastid-specific ribosomal proteins. [RR19_SPIOL] This protein binds directly to 16S ribosomal RNA.[2] [RR12_SPIOL] With S4 and S5 plays an important role in translational accuracy. Located at the interface of the 30S and 50S subunits (By similarity).[HAMAP-Rule:MF_00403_B] [RK20_SPIOL] 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] [RK21_SPIOL] This protein binds to 23S ribosomal RNA in the presence of protein L20 (By similarity). [RR9_SPIOL] Binds directly to 16S ribosomal RNA.[3] [:] [RR6_SPIOL] Binds together with S18 to 16S ribosomal RNA (By similarity).[UniProtKB:O78447] [RK34_SPIOL] This protein binds directly to 23S ribosomal RNA (By similarity). [PRSP1_SPIOL] A ribosome-binding factor that may be involved in an unknown stress response. Modeling onto the 70S spinach chloroplast ribosome and its position in the E.coli 70S ribosome suggests it binds in the decoding region of the 30S ribosomal subunit, precluding the binding of tRNA to the ribosome. Its position is incompatible with translation. Upon expression in E.coli binds to 30S and 70S ribosomes, decreases binding of tRNA(fMet). Stabilizes 70S ribosomes against dissociation. May be recycled by the combined action of ribosome-recycling factor (RRF) and EF-G.[4] [RR1_SPIOL] Component of the chloroplast ribosome (chloro-ribosome), a dedicated translation machinery responsible for the synthesis of chloroplast genome-encoded proteins, including proteins of the transcription and translation machinery and components of the photosynthetic apparatus (PubMed:10874039, PubMed:28007896). Actively engaged in the initiation complex formation via a strong mRNA-binding activity. Possesses a poly(A)-binding activity which might play a role as a control element in chloroplast mRNA translation (PubMed:1527032).[5] [6] [7] [RK5_SPIOL] Binds 5S rRNA, forms part of the central protuberance of the 50S subunit (By similarity). [RR8_SPIOL] 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] [RR14_SPIOL] Binds 16S rRNA, required for the assembly of 30S particles (By similarity).[:] [RR7_SPIOL] 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 (By similarity).[HAMAP-Rule:MF_00480] [RR13_SPIOL] Located at the top of the head of the 30S subunit, it contacts several helices of the 16S rRNA.[HAMAP-Rule:MF_01315] [RR4_SPIOL] One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it nucleates assembly of the body of the 30S subunit (By similarity).[HAMAP-Rule:MF_01306] With S5 and S12 plays an important role in translational accuracy (By similarity).[HAMAP-Rule:MF_01306] Publication Abstract from PubMedChloroplastic translation is mediated by a bacterial-type 70S chloroplast ribosome. During the evolution, chloroplast ribosomes have acquired five plastid-specific ribosomal proteins or PSRPs (cS22, cS23, bTHXc, cL37 and cL38) which have been suggested to play important regulatory roles in translation. However, their exact locations on the chloroplast ribosome remain elusive due to lack of a high-resolution structure, hindering our progress to understand their possible roles. Here we present a cryo-EM structure of the 70S chloroplast ribosome from spinach resolved to 3.4 A and focus our discussion mainly on the architecture of the 30S small subunit (SSU) which is resolved to 3.7 A. cS22 localizes at the SSU foot where it seems to compensate for the deletions in 16S rRNA. The mRNA exit site is highly remodeled due to the presence of cS23 suggesting an alternative mode of translation initiation. bTHXc is positioned at the SSU head and appears to stabilize the intersubunit bridge B1b during thermal fluctuations. The translation factor plastid pY binds to the SSU on the intersubunit side and interacts with the conserved nucleotide bases involved in decoding. Most of the intersubunit bridges are conserved compared to the bacteria, except for a new bridge involving uL2c and bS6c. Unique localization of the plastid-specific ribosomal proteins in the chloroplast ribosome small subunit provides mechanistic insights into the chloroplastic translation.,Ahmed T, Shi J, Bhushan S Nucleic Acids Res. 2017 Aug 21;45(14):8581-8595. doi: 10.1093/nar/gkx499. PMID:28582576[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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