5x8t | pdb_00005x8t
Structure of the 50S large subunit of chloroplast ribosome from spinach
Structural highlights
Function[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. [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. [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). [RK14_SPIOL] Binds to 23S rRNA (By similarity). [RK23_SPIOL] Binds to 23S rRNA (By similarity). Located at the polypeptide exit tunnel on the outside of the subunit. [RK34_SPIOL] This protein binds directly to 23S ribosomal RNA (By similarity). [RK5_SPIOL] Binds 5S rRNA, forms part of the central protuberance of the 50S subunit (By similarity). [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. 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[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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