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| {{STRUCTURE_3bbo| PDB=3bbo | SCENE= }} | | {{STRUCTURE_3bbo| PDB=3bbo | SCENE= }} |
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| '''Homology model for the Spinach chloroplast 50S subunit fitted to 9.4A cryo-EM map of the 70S chlororibosome'''
| | ===Homology model for the Spinach chloroplast 50S subunit fitted to 9.4A cryo-EM map of the 70S chlororibosome=== |
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| ==Overview==
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| 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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_18042701}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 18042701 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_18042701}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Ribonucleoprotein particle]] | | [[Category: Ribonucleoprotein particle]] |
| [[Category: Spinach chloroplast ribosome]] | | [[Category: Spinach chloroplast ribosome]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed May 28 09:19:16 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 03:24:18 2008'' |
