12,696 research outputs found

    Mapping of the saccharomyces cerevisiae oxa1-mitochondrial ribosome interface and identification of MrpL40, a ribosomal protein in close proximity to oxal and critical for oxidative phosphorylation complex assembly

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    The Oxa1 protein plays a central role in facilitating the cotranslational insertion of the nascent polypeptide chains into the mitochondrial inner membrane. Mitochondrially encoded proteins are synthesized on matrix-localized ribosomes which are tethered to the inner membrane and in physical association with the Oxa1 protein. In the present study we used a chemical cross-linking approach to map the Saccharomyces cerevisiae Oxa1-ribosome interface, and we demonstrate here a close association of Oxa1 and the large ribosomal subunit protein, MrpL40. Evidence to indicate that a close physical and functional relationship exists between MrpL40 and another large ribosomal protein, the Mrp20/L23 protein, is also provided. MrpL40 shares sequence features with the bacterial ribosomal protein L24, which like Mrp20/L23 is known to be located adjacent to the ribosomal polypeptide exit site. We propose therefore that MrpL40 represents the Saccharomyces cerevisiae L24 homolog. MrpL40, like many mitochondrial ribosomal proteins, contains a C-terminal extension region that bears no similarity to the bacterial counterpart. We show that this C-terminal mitochondria-specific region is important for MrpL40's ability to support the synthesis of the correct complement of mitochondrially encoded proteins and their subsequent assembly into oxidative phosphorylation complexes

    Mrpl35, A Mitospecific Component of Mitoribosomes, Plays A Key Role in Cytochrome \u3cem\u3eC\u3c/em\u3e Oxidase Assembly

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    Mitoribosomes perform the synthesis of the core components of the oxidative phosphorylation (OXPHOS) system encoded by the mitochondrial genome. We provide evidence that MrpL35 (mL38), a mitospecific component of the yeast mitoribosomal central protuberance, assembles into a subcomplex with MrpL7 (uL5), Mrp7 (bL27), and MrpL36 (bL31) and mitospecific proteins MrpL17 (mL46) and MrpL28 (mL40). We isolated respiratory defective mrpL35 mutant yeast strains, which do not display an overall inhibition in mitochondrial protein synthesis but rather have a problem in cytochrome coxidase complex (COX) assembly. Our findings indicate that MrpL35, with its partner Mrp7, play a key role in coordinating the synthesis of the Cox1 subunit with its assembly into the COX enzyme and in a manner that involves the Cox14 and Coa3 proteins. We propose that MrpL35 and Mrp7 are regulatory subunits of the mitoribosome acting to coordinate protein synthesis and OXPHOS assembly events and thus the bioenergetic capacity of the mitochondria

    Nonstandard electroconvection in a bent-core oxadiazole material

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    Electroconvection (EC) phenomena have been investigated in the nematic phase of a bent-core oxadiazole material with negative dielectric anisotropy and a frequency dependent conductivity anisotropy. The formation of longitudinal roll (LR) patterns is one of the predominant features observed in the complete frequency and voltage range studied. At voltages much above the LR threshold, various complex patterns such as the "crisscrossed" pattern, bimodal varicose, and turbulence are observed. Unusually, the nonstandard EC (ns-EC) instability in this material, is observed in a regime in which we measure the dielectric and conductivity anisotropies to be negative and positive respectively. A further significant observation is that the EC displays distinct features in the high and low temperature regimes of the nematic phase, supporting an earlier report that EC patterns could distinguish between regions that have been reported as uniaxial and biaxial nematic phases