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-Structure paper
Title | Cryo-EM study of the spinach chloroplast ribosome reveals the structural and functional roles of plastid-specific ribosomal proteins. |
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Journal, issue, pages | Proc Natl Acad Sci U S A, Vol. 104, Issue 49, Page 19315-19320, Year 2007 |
Publish date | Dec 4, 2007 |
Authors | Manjuli R Sharma / Daniel N Wilson / Partha P Datta / Chandana Barat / Frank Schluenzen / Paola Fucini / Rajendra K Agrawal / |
PubMed Abstract | Protein synthesis in the chloroplast is carried out by chloroplast ribosomes (chloro-ribosome) and regulated in a light-dependent manner. Chloroplast or plastid ribosomal proteins (PRPs) generally ...Protein synthesis in the chloroplast is carried out by chloroplast ribosomes (chloro-ribosome) and regulated in a light-dependent manner. Chloroplast or plastid ribosomal proteins (PRPs) generally are larger than their bacterial counterparts, and chloro-ribosomes contain additional plastid-specific ribosomal proteins (PSRPs); however, it is unclear to what extent these proteins play structural or regulatory roles during translation. We have obtained a three-dimensional cryo-EM map of the spinach 70S chloro-ribosome, revealing the overall structural organization to be similar to bacterial ribosomes. Fitting of the conserved portions of the x-ray crystallographic structure of the bacterial 70S ribosome into our cryo-EM map of the chloro-ribosome reveals the positions of PRP extensions and the locations of the PSRPs. Surprisingly, PSRP1 binds in the decoding region of the small (30S) ribosomal subunit, in a manner that would preclude the binding of messenger and transfer RNAs to the ribosome, suggesting that PSRP1 is a translation factor rather than a ribosomal protein. PSRP2 and PSRP3 appear to structurally compensate for missing segments of the 16S rRNA within the 30S subunit, whereas PSRP4 occupies a position buried within the head of the 30S subunit. One of the two PSRPs in the large (50S) ribosomal subunit lies near the tRNA exit site. Furthermore, we find a mass of density corresponding to chloro-ribosome recycling factor; domain II of this factor appears to interact with the flexible C-terminal domain of PSRP1. Our study provides evolutionary insights into the structural and functional roles that the PSRPs play during protein synthesis in chloroplasts. |
External links | Proc Natl Acad Sci U S A / PubMed:18042701 / PubMed Central |
Methods | EM (single particle) |
Resolution | 9.4 Å |
Structure data | EMDB-1417: Cryo-EM study of the Spinach chloroplast ribosome reveals the structural and functional roles of plastid-specific ribosomal proteins |
Source |
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Keywords | RIBOSOME / SMALL RIBOSOMAL SUBUNIT / SPINACH CHLOROPLAST RIBOSOME / RIBONUCLEOPROTEIN PARTICLE / MACROMOLECULAR COMPLEX |