5mmi
From Proteopedia
Structure of the large subunit of the chloroplast ribosome
Structural highlights
Function[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] [RK11_SPIOL] This protein binds directly to 23S ribosomal RNA (By similarity). [RK21_SPIOL] This protein binds to 23S ribosomal RNA in the presence of protein L20 (By similarity). [RK19_SPIOL] Located at the 30S-50S ribosomal subunit interface and binds directly to 23S ribosomal RNA (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. [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). Publication Abstract from PubMedChloroplasts are cellular organelles of plants and algae that are responsible for energy conversion and carbon fixation by the photosynthetic reaction. As a consequence of their endosymbiotic origin, they still contain their own genome and the machinery for protein biosynthesis. Here, we present the atomic structure of the chloroplast 70S ribosome prepared from spinach leaves and resolved by cryo-EM at 3.4 A resolution. The complete structure reveals the features of the 4.5S rRNA, which probably evolved by the fragmentation of the 23S rRNA, and all five plastid-specific ribosomal proteins. These proteins, required for proper assembly and function of the chloroplast translation machinery, bind and stabilize rRNA including regions that only exist in the chloroplast ribosome. Furthermore, the structure reveals plastid-specific extensions of ribosomal proteins that extensively remodel the mRNA entry and exit site on the small subunit as well as the polypeptide tunnel exit and the putative binding site of the signal recognition particle on the large subunit. The translation factor pY, involved in light- and temperature-dependent control of protein synthesis, is bound to the mRNA channel of the small subunit and interacts with 16S rRNA nucleotides at the A-site and P-site, where it protects the decoding centre and inhibits translation by preventing tRNA binding. The small subunit is locked by pY in a non-rotated state, in which the intersubunit bridges to the large subunit are stabilized. The complete structure of the chloroplast 70S ribosome in complex with translation factor pY.,Bieri P, Leibundgut M, Saurer M, Boehringer D, Ban N EMBO J. 2016 Dec 22. pii: e201695959. doi: 10.15252/embj.201695959. PMID:28007896[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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