Protein synthesis respiratory

Qiapter 8 indicates that oxidant air pollutants may adversely affect the olfactory and sight senses, degree of activity, general health and vigor, reproductive rate, heart and kidney function, protein synthesis, respiratory function, and disease resistance in domestic vertebrates under laboratory conditions. Many of these adverse physical responses develop at or near the concentrations of ozone currently experienced daily in ambient air in parts of the San Bernardino Mountains. 

Not all the cellular DNA is in the nucleus some is found in the mitochondria. In addition, mitochondria contain RNA as well as several enzymes used for protein synthesis. Interestingly, mitochond-rial RNA and DNA bear a closer resemblance to the nucleic acid of bacterial cells than they do to animal cells. For example, the rather small DNA molecule of the mitochondrion is circular and does not form nucleosomes. Its information is contained in approximately 16,500 nucleotides that func-tion in the synthesis of two ribosomal and 22 transfer RNAs (tRNAs). In addition, mitochondrial DNA codes for the synthesis of 13 proteins, all components of the respiratory chain and the oxidative phosphorylation system. Still, mitochondrial DNA does not contain sufficient information for the synthesis of all mitochondrial proteins most are coded by nuclear genes. Most mitochondrial proteins are synthesized in the cytosol from nuclear-derived messenger RNAs (mRNAs) and then transported into the mito-chondria, where they contribute to both the structural and the functional elements of this organelle. Because mitochondria are inherited cytoplasmically, an individual does not necessarily receive mitochondrial nucleic acid equally from each parent. In fact, mito-chondria are inherited maternally. 

K3. King, M. P., Koga, Y., Davidson, M., and Schon, E. A., Defects in mitochondrial protein synthesis and respiratory chain activity segregate with the tRNALe (UUR> mutation associated with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes. Mol. Cell. Biol. 12, 480-490 (1992). 

At present, direct evidence for the redox control of organellar gene expression, as predicted CORR, is stronger for chloroplasts than for mitochondria (Pfannschmidt et al. 1999). Redox effects on mitochondrial gene expression in vitro are largely confined, at present, to protein synthesis (Allen et al. 1995 Galvis et al. 1998). The search for a direct signalling pathway from the respiratory chain to mitochondrial DNA is likely to be an active area of future research (Allen et al. 2005 Lane 2005). 

Answer In (a), respiratory control by ADP, the increase in respiratory rate is limited by the rate of diffusion of ADP, and the response would be expected to occur in fractions of a millisecond. The adjustment to (b), hypoxia mediated by HIF-1, requires a change in concentration of several proteins, the result of increased synthesis or degradation. The time scale for protein synthesis or degradation is typically many seconds to hours—much longer than the time required for changes in substrate concentration. 

Mutations in tRNALeu n UR) may be expected to have an important effect on protein synthesis in mitochondria. The MELAS-associated human mitochondrial tRNALeu <[ UR) mutation causes aminoacylation deficiency and a concomitant defect in translation initiation (Borner et al., 2000). The expected result would be a deficit in general mitochondrial protein synthesis with resulting deficiencies of multiple OXPHOS components. Patients with MELAS disorder have been found to have a marked decrease in the activity of respiratory Complex I with a secondary reduction in the activity of Complex IV... 

Cethromycin (ABT-773) 39 (Advanced Life Sciences) had an NDA filed in October 2008 for the treatment of CAP.67 Advanced Life Sciences is also evaluating cethromycin 39 against other respiratory tract infections and in pre-clinical studies as a prophylactic treatment of anthrax post-exposure. Cethromycin 3968 70 is a semi-synthetic ketolide derivative of erythromycin 4071 originally synthesised by Abbott Laboratories,72 which like erythromycin 40, inhibits bacterial protein synthesis through binding to the peptidyl-transferase site of the bacterial 50S ribosomal subunit. Important macrolide antibiotics in clinical use today include erythromycin 40 itself, clarithromycin, azithromycin and, most recently, telithromycin (launched in 2001). 

Protein synthesis = dpm (xlO ) per mg soluble protein per hr, oxygen consumption = nmoles (xl(P) of O2 consumed per mg mitochondrial protein per hr RNA-P/DNA P = pg RNA-P per pg DNA-P. Values are meanlSEM. In the figure for mitochondrial respiration, the horizontal line labeled CC"+CA denotes the respiratory level attained by animals cardiacectomized-allatectomized at day 0 the darkened area at days 4-6 denotes the period of maximal heme synthesis. 

Although a few subunits of mitochondrial membrane proteins are coded by mitochondrial DNA and synthesized in the mitochondrial matrix, most membrane proteins including the adenine nucleotide carrier are coded by nuclear genes and synthesized on cytoplasmic ribosomes [80,81], Chloramphenicol, an inhibitor of mitochondrial protein synthesis, does not inhibit incorporation of radioactive leucine into the carrier in growing Neurospora crassa, but cycloheximide, an inhibitor of cytoplasmic protein synthesis, does inhibit leucine incorporation [78]. Also, a yeast nuclear respiratory mutant has been shown to cause a defect in adenine nucleotide transport [81], and the nuclear gene responsible for coding the carrier in yeast is currently being cloned for further studies [82]. 

Chloramphenicol and florfenicol act by binding to the 50S ribosomal subunit and blocking transfer RNA, inhibiting bacterial protein synthesis. They are considered bacteriostatic, but the MBCs of florfenicol for some respiratory pathogens are low enough to consider it bactericidal. 

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