5x8r
From Proteopedia
Structure of the 30S small subunit of chloroplast ribosome from spinach
Structural highlights
Function[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] [RRP3_SPIOL] One of the plastid-specific ribosomal proteins. [RR9_SPIOL] Binds directly to 16S ribosomal RNA.[1] [:] [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).[2] [3] [4] [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] [RRP2_SPIOL] May have a role in the recruitment of stored chloroplast mRNAs for active protein synthesis.[5] [RR19_SPIOL] This protein binds directly to 16S ribosomal RNA.[6] [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] [RR5_SPIOL] Binds directly to 16S ribosomal RNA. Involved in spectinomycin and neamine resistance and streptomycin independence.[:] [RR6_SPIOL] Binds together with S18 to 16S ribosomal RNA (By similarity).[UniProtKB:O78447] [RR14_SPIOL] Binds 16S rRNA, required for the assembly of 30S particles (By similarity).[:] [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] [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.[7] [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] 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. See AlsoReferences
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