Mitochondrial assembly in yeast

Abstract

The yeast Saccharomyces cerevisiae is likely to be the first organism for which a complete inventory of mitochondrial proteins and their functions can be drawn up. A survey of the 340 or so proteins currently known to be localised in yeast mitochondria reveals the considerable investment required to maintain the organelle's own genetic system, which itself contributes seven key components of the electron transport chain. Translation and respiratory complex assembly are particularly expensive processes, together requiring around 150 of the proteins so far known. Recent developments in both areas are reviewed and approaches to the identification of novel mitochondrial proteins are discussed.z 1999 Federation of European Biochemical Societies.

The Effect of RNA Interference Down-regulation of RNA Editing 3′-Terminal Uridylyl Transferase (TUTase) 1 on Mitochondrial de Novo Protein Synthesis and Stability of Respiratory Complexes in Trypanosoma brucei

“…In yeast with defective mitochondrial protein synthesis, nuclear-encoded subunits of respiratory complexes III and IV continue to be synthesized and imported into the mitochondrion, but assembly of the complexes is impaired (40). In addition, a specific nuclear mutation (PET309) affecting the synthesis of Cox1p in yeast resulted in an increased proteolytic degradation of other mitochondrial and nuclear subunits (41,42); interference with binding of mRNA-specific activators (43,44) prevented membrane tethering of these mRNAs and induced increased turn-over of the newly synthesized polypeptides (45). In mammalian cells in which mitochondrial protein synthesis was blocked by ethidium bromide, the synthesis of nuclear-encoded subunits of complexes I, III, and IV was not affected, but the proteins were rapidly degraded (46,47).…”

Genomics-based dissection of the cross-talk of chloroplasts with the nucleus and mitochondria in Arabidopsis

“…(iv) Post-translational events, such as the assembly of the multi-protein complexes of the thylakoid membrane or of the inner envelope of mitochondria. These processes require nuclear-encoded assembly factors (Grivell et al, 1999;Vothknecht and Westhoff, 2001). (v) Organelle development, for instance organelle division, which is tightly controlled by nuclear-encoded proteins (Osteryoung and Nunnari, 2003).…”

Pet111p, an Inner Membrane-bound Translational Activator That Limits Expression of the Saccharomyces cerevisiaeMitochondrial Gene COX2

“…3 This behavior contrasts with that of overproduced Pet309p, the COX1 mRNA-specific activator, that spans the inner membrane and is accessible to protease from the outside (12).…”

“…The key products of mitochondrial gene expression are integral membrane proteins that are assembled with proteins encoded by nuclear genes to form energy-transducing complexes in the inner membrane (1)(2)(3). Thus, the activity of mitochondrial genetic systems must be coordinated with cellular gene expression and adapted for efficient delivery of hydrophobic proteins to the inner membrane.…”

“…Genetic analysis has revealed that the activator proteins functionally interact with the 5Ј-UTLs 1 of their target mRNAs and probably mediate productive interactions between those mRNAs and ribosomes (4,5). As discussed below, several of the activator proteins have been found to be associated with mitochondrial membranes, suggesting that they could function to localize the synthesis of hydrophobic mitochondrial gene products to their sites of insertion in the inner membrane (3,4,6,7). This hypothesis is strongly supported by the fact that the untranslated regions of the COX2 and COX3 mRNAs contain information that facilitates correct targeting of the Cox2p and Cox3p cytochrome oxidase subunits (8).…”