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-Structure paper
| タイトル | Chloroplast-encoded small subunit extensions reshape the Chlamydomonas chlororibosome. |
|---|---|
| ジャーナル・号・ページ | bioRxiv, Year 2026 |
| 掲載日 | 2026年2月9日 |
 著者 | Florent Waltz / Philippe A Lehner / Philippe Van der Stappen / Lukas Kater / Stefan Pfeffer / Benjamin D Engel /   |
| PubMed 要旨 | Chloroplast ribosomes (chlororibosomes) synthesize the core protein components of the photosynthetic apparatus, yet their structural diversity outside flowering plants remains largely unexplored. ...Chloroplast ribosomes (chlororibosomes) synthesize the core protein components of the photosynthetic apparatus, yet their structural diversity outside flowering plants remains largely unexplored. Here, we combine in situ cryo-electron tomography (cryo-ET) with single-particle cryo-electron microscopy (cryo-EM) to determine the structure of the chlororibosome from the unicellular green alga . Subtomogram averaging of chlororibosomes in their native environment, resolved to ~5 Å resolution and in distinct translational states, reveals particles both free in the stroma and loosely tethered to thylakoid membranes. These reconstructions uncover an additional "arm" domain on the small subunit. High-resolution single-particle reconstruction of isolated chlororibosomes to ~2.5 Å, in states bound either to the inhibitory translation factor pY or to a nascent chain-linked P-site tRNA, reveals that this domain is built primarily from extensive chloroplast-encoded insertions and extensions of conserved small subunit proteins, supported by chlororibosome-specific ribosomal proteins. The arm domain is located around the mRNA entry and exit channels, suggesting a role in stabilizing the mRNA trajectory through the small subunit and organizing chloroplast polysomes. Together, these data reveal unexpected structural variation of algal chlororibosomes and suggest that chloroplast translation has diversified substantially even among relatively closely related photosynthetic lineages. |
 リンク | bioRxiv / PubMed:41727112 / PubMed Central |
| 手法 | EM (サブトモグラム平均) / EM (単粒子) |
| 解像度 | 2.45 - 9.29 Å |
| 構造データ |  EMDB-56139: Subtomogram average of the Chlamydomonas reinhardtii chlororibosome - consensus map  EMDB-56140: Subtomogram average of the Chlamydomonas reinhardtii chlororibosome - LSU focused  EMDB-56141: Subtomogram average of the Chlamydomonas reinhardtii chlororibosome - SSU focused  EMDB-56142: Subtomogram average of the Chlamydomonas reinhardtii chlororibosome - SSU extension focused  EMDB-56143: Subtomogram average of the Chlamydomonas reinhardtii chlororibosome - chimeric map  EMDB-56144: Subtomogram average of the membrane-bound Chlamydomonas reinhardtii chlororibosome  EMDB-56337: Structure of the Chlamydomonas reinhardtii chlororibosome - consensus map  EMDB-56338: Structure of the Chlamydomonas reinhardtii chlororibosome - LSU focus  EMDB-56339: Structure of the Chlamydomonas reinhardtii chlororibosome - LSU CP focus  EMDB-56340: Structure of the Chlamydomonas reinhardtii chlororibosome - LSU L7/12 stalk focus  EMDB-56341: Structure of the Chlamydomonas reinhardtii chlororibosome - SSU body focus  EMDB-56342: Structure of the Chlamydomonas reinhardtii chlororibosome - SSU head focus  EMDB-56344: Structure of the Chlamydomonas reinhardtii chlororibosome - SSU head extension recenter and focus  EMDB-56349: Structure of the Chlamydomonas reinhardtii chlororibosome - SSU extension focus EMDB-56352, PDB-9tvu:  EMDB-56560: Structure of the Chlamydomonas reinhardtii chlororibosome with pY factor - consensus map  EMDB-56561: Structure of the Chlamydomonas reinhardtii chlororibosome with P-site tRNA - consensus map  EMDB-56562: Structure of the Chlamydomonas reinhardtii chlororibosome with P-site tRNA - LSU focus  EMDB-56563: Structure of the Chlamydomonas reinhardtii chlororibosome with pY factor - LSU focus  EMDB-56564: Structure of the Chlamydomonas reinhardtii chlororibosome with pY factor - focus SSU  EMDB-56565: Structure of the Chlamydomonas reinhardtii chlororibosome with P-site tRNA - focus SSU EMDB-56567, PDB-28jw: EMDB-56602, PDB-28lu: |
| 化合物 |  ChemComp-MG:  ChemComp-K:  ChemComp-CLM: |
| 由来 |
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 キーワード | RIBOSOME / chloroplast / translation / chlororibosome |
chlamydomonas reinhardtii (クラミドモナス)