Open AccessCryo-EM structure of the large subunit of the spinach chloroplast ribosome
Author(s) -
Tofayel Ahmed,
Zhan Yin,
Shashi Bhushan
Publication year - 2016
Publication title -
scientific reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.24
H-Index - 213
ISSN - 2045-2322
DOI - 10.1038/srep35793
Subject(s) - ribosome , eukaryotic ribosome , ribosomal rna , ribosomal protein , a site , chloroplast , ribosome profiling , biology , protein subunit , eukaryotic large ribosomal subunit , 50s , biochemistry , rna , binding site , gene
Protein synthesis in the chloroplast is mediated by the chloroplast ribosome (chloro-ribosome). Overall architecture of the chloro-ribosome is considerably similar to the Escherichia coli ( E. coli) ribosome but certain differences are evident. The chloro-ribosome proteins are generally larger because of the presence of chloroplast-specific extensions in their N- and C-termini. The chloro-ribosome harbours six plastid-specific ribosomal proteins (PSRPs); four in the small subunit and two in the large subunit. Deletions and insertions occur throughout the rRNA sequence of the chloro-ribosome (except for the conserved peptidyl transferase center region) but the overall length of the rRNAs do not change significantly, compared to the E. coli . Although, recent advancements in cryo-electron microscopy (cryo-EM) have provided detailed high-resolution structures of ribosomes from many different sources, a high-resolution structure of the chloro-ribosome is still lacking. Here, we present a cryo-EM structure of the large subunit of the chloro-ribosome from spinach ( Spinacia oleracea ) at an average resolution of 3.5 Å. High-resolution map enabled us to localize and model chloro-ribosome proteins, chloroplast-specific protein extensions, two PSRPs (PSRP5 and 6) and three rRNA molecules present in the chloro-ribosome. Although comparable to E. coli , the polypeptide tunnel and the tunnel exit site show chloroplast-specific features.