Yeast mitochondria

Xanthothricin 308 stimulated oxidation of NADH and NAD-linked substrates by rat liver mitochondria, yeast mitochondria, and Ehrlich ascites tumor cells (74MI1, 74MI3). It also stimulated mitochondrial oxidation of succinate, pyruvate, or malate. The antibiotic xanthothricin was obtained... 

Figure 3 The ubiquitous mechanism of [cpn60]i4. Purified [cpn60]i4 from E, coli. Pea chloroplasts (pea cp) and yeast mitochondria (yeast mt) were assayed in vitro for their ability to reconstitute R. rubrum Rubisco in the presence (+) or absence (-) of . coli cpnlO and Mg-ATP as in ref (22). a) Percent reconstitution after one hour assay, measured as in Figure 2a, normalized to the . coli cpn60 standard reconstitution reaction, b) Summary of the reaction conditions.

Fig. 3. Secondary structure comparison between the RNA molecules from the small ribosomal subunits of human mitochondrion, E. coli, and yeast (Brimacombe, 1983). Relations between a, b, and c are as in Fig. 2.

Williams and Keeling 2002). We also suggest that this close association of the mitochondrion-like organelle and endomembrane system facilitates the assembly of cytosolic Rlil, the only known essential FeS protein for yeast viability (Iill et al. 2005 reviewed in Tachezy and Dolezal 2007). These data are consistent with previous hypotheses that the primary function of the mitochondrion-like organelle in C. parvum is the assembly of FeS clusters in order to provide mature FeS proteins to all cellular compartments, including the cytosol, mitochondrion, and nucleus. 

Mitochondria are present in all eukaryotic cells that use oxygen in respiration, but the number per cell and the form and size vary.1-4 Certain tiny trypanosomes have just one mitochondrion but some oocytes have as many as 3 x 105. Mammalian cells typically contain several hundred mitochondria and liver cells5 more than 1000. Mammalian sperm cells may contain 50-75 mitochondria,6 but in some organisms only one very large helical mitochondrion, formed by the fusion of many individual mitochondria, wraps around the base of the tail. Typical mitochondria appear to be about the size of cells of E. coli. However, study of ultrathin serial sections of a single yeast cell by electron microscopy has shown that, under some growth conditions, all of the mitochondria are interconnected.7... 

Baker s yeast contains at least four lactate dehydrogenases, three of which are located in the mitochondrion and one in the cytoplasm (Table 1). Electron flow in the mitochondrial enzymes is linked to cytochromes rather than nicotinamides. Their apparent physiological function is the reversible interconversion of pyruvate and lactate, and it is not clear whether any of these four enzymes accept ketones other than pyruvate, which would limit their importance in organic synthesis. 

In anaerobic conditions, cells can metabolize pyruvate to lactate or to ethanol plus CO2 (in the case of yeast), with the reoxidation of NADH. In aerobic conditions, pyruvate is transported into the mitochondrion, where pyruvate dehydrogenase converts it into acetyl CoA and CO2 (see Figure 8-5). 

Since roughly 1000 stuck translocation intermediates can be observed in a typical yeast mitochondrion, it is thought that mitochondria have approximately 1000 general import pores for the uptake of mitochondrial proteins. 

HOS. Because R. sphaeroides is a member of the class of proteobacteria from which the mitochondrion is thought to have developed, both HOS and HAS (as well as the catalytic subunits of CcO) share a high degree of sequence homology with their eukaryotic counterparts. Thus, what we observe in R. sphaeroides may very well be more generally applicable to include eukaryotic organisms. However, no direct interaction has yet been observed in yeast between HOS and HAS despite numerous attempts, and any extrapolation between the work reported here and potential interactions between eukaryotic HOS and HAS must therefore be treated with caution. 

Fig. 16.2 Diagram of an electron micrograph of a section through a resting cell of bakers yeast Saccharomyces certvisiae). ER, endoplasmic reticulum M, mitochondrion N, nucleus Nm, nuclear membrane Nn, nucleolus Pi, invagination PI, plasmalemma V, vacuole Vp, polymetaphosphate granule W, cell wall Ws, bud scar L, lipid granule (sphaerosome).

Hoffmann, H.P., Avers, C.J. Mitochondrion of yeast Ultrastructural evidence for one giant, branched organelle per cell. Science 181, 749-751 (1973)... 

A Role for the Mitochondrion and Reactive Oxygen Species in Oxygen Sensing and Adaptation to Hypoxia in Yeast... 

---