| 1. |
- Dunham, Christine M., et al.
(författare)
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Structures of tRNAs with an expanded anticodon loop in the decoding center of the 30S ribosomal subunit
- 2007
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Ingår i: RNA. - : Cold Spring Harbor Laboratory. - 1355-8382 .- 1469-9001. ; 13:6, s. 817-823
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Tidskriftsartikel (refereegranskat)abstract
- During translation, some +1 frameshift mRNA sites are decoded by frameshift suppressor tRNAs that contain an extra base in their anticodon loops. Similarly engineered tRNAs have been used to insert nonnatural amino acids into proteins. Here, we report crystal structures of two anticodon stem–loops (ASLs) from tRNAs known to facilitate +1 frameshifting bound to the 30S ribosomal subunit with their cognate mRNAs. ASLCCCG and ASLACCC (5'–3' nomenclature) form unpredicted anticodon–codon interactions where the anticodon base 34 at the wobble position contacts either the fourth codon base or the third and fourth codon bases. In addition, we report the structure of ASLACGA bound to the 30S ribosomal subunit with its cognate mRNA. The tRNA containing this ASL was previously shown to be unable to facilitate +1 frameshifting in competition with normal tRNAs (Hohsaka et al. 2001), and interestingly, it displays a normal anticodon–codon interaction. These structures show that the expanded anticodon loop of +1 frameshift promoting tRNAs are flexible enough to adopt conformations that allow three bases of the anticodon to span four bases of the mRNA. Therefore it appears that normal triplet pairing is not an absolute constraint of the decoding center.
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| 2. |
- Krengel, Ute, 1964, et al.
(författare)
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Preliminary X-ray crystallographic analysis of the secreted chorismate mutase from Mycobacterium tuberculosis: A tricky crystallization problem solved
- 2006
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Ingår i: Acta Crystallographica Section F: Structural Biology and Crystallization Communications. - 1744-3091. ; 62:5, s. 441-445
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Tidskriftsartikel (refereegranskat)abstract
- Chorismate mutase catalyzes the conversion of chorismate to prephenate in the biosynthesis of the aromatic amino acids tyrosine and phenylalanine in bacteria, fungi and plants. Here, the crystallization of the unusual secreted chorismate mutase from Mycobacterium tuberculosis (encoded by Rv1885c), a 37.2 kDa dimeric protein belonging to the AroQγ subclass of mutases, is reported. Crystal optimization was non-trivial and is discussed in detail. To obtain crystals of sufficient quality, it was critical to initiate crystallization at higher precipitant concentration and then transfer the drops to lower precipitant concentrations within 5-15 min, in an adaptation of a previously described technique [Saridakis & Chayen (2000), Protein Sci. 9, 755-757]. As a result of the optimization, diffraction improved from 3.5 to 1.3 Å resolution. The crystals belong to space group P21, with unit-cell parameters a = 42.6, b = 72.6, c = 62.0 Å., β = 104.5°. The asymmetric unit contains one biological dimer, with 167 amino acids per protomer. A soak with a transition-state analogue is also described.
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| 3. |
- Mathews, T.S, et al.
(författare)
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Integration of functional reliability analysis with hardware reliability : An application to safety grade decay heat removal system of Indian 500 MWe PFBR
- 2009
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 36:4, s. 481-492
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Tidskriftsartikel (refereegranskat)abstract
- A passive system can fail either due to classical mechanical failure of components, referred to as hardware failure, or due to the failure of physical phenomena to fulfill the intended function, referred to as functional failure. In this paper a methodology is discussed for the integration of these two kinds of unreliability and applied to evaluate the integrated failure probability of the passive decay heat removal system of Indian 500 MWe prototype fast breeder reactor (PFBR). The probability of occurrence of various system hardware configurations is evaluated using the fault tree method and functional failure probabilities on the corresponding configurations are determined based on the overall approach reported in the reliability methods for passive system (RMPS) project. The variation of functional reliability with time, which is coupled to the probability of occurrence of various hardware system configurations is studied and incorporated in the integrated reliability analysis. It is observed that this consideration of the dependence of functional reliability on time will give significant advantages on system reliability. The integrated reliability analysis is also explained using an event tree. The impact of the provision for forced circulation in the primary circuit on functional reliability is also studied with this procedure and it is found that the forced circulation capability helps to bring down the total decay heat removal failure probability by lowering the peak temperatures after the reactor shut down.
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| 4. |
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| 5. |
- Weixlbaumer, Albert, et al.
(författare)
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Crystal structure of the ribosome recycling factor bound to the ribosome
- 2007
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 14:8, s. 733-737
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Tidskriftsartikel (refereegranskat)abstract
- In bacteria, disassembly of the ribosome at the end of translation is facilitated by an essential protein factor termed ribosome recycling factor (RRF), which works in concert with elongation factor G. Here we describe the crystal structure of the Thermus thermophilus RRF bound to a 70S ribosomal complex containing a stop codon in the A site, a transfer RNA anticodon stem-loop in the P site and tRNAfMet in the E site. The work demonstrates that structures of translation factors bound to 70S ribosomes can be determined at reasonably high resolution. Contrary to earlier reports, we did not observe any RRF-induced changes in bridges connecting the two subunits. This suggests that such changes are not a direct requirement for or consequence of RRF binding but possibly arise from the subsequent stabilization of a hybrid state of the ribosome.
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