Anaerobic polypeptides

After approximately 90 min of anoxia, the induced synthesis of an additional group of c. 20 polypeptides is first detected. This group of 20 anaerobic polypeptides (ANPs) represents more than 70% of the total labelled amino acid incorporation after five hours of anaerobiosis (Fig. 3). By this time the synthesis of the TPs is at a minimal level however, these polypeptides accumulate to a high level during early anaerobiosis and have been shown by pulse-chase experiments to be very stable. The synthesis of... 

Many plant species synthesise ANPs in response to anaerobic conditions. The most easily assayed feature, the induction of ADH by low oxygen tension, has been widely demonstrated. Induction of the anaerobic polypeptides and the cessation of aerobic protein synthesis has been shown to occur in maize, cotton and, to a lesser extent, soybean (Russell et al., 1990). That the DNA signals specifying anaerobic induction are... 

Anaerobic treatment results in a drastic alteration in the pattern of protein synthesis in maize seedlings (Sachs, Freeling Okimoto, 1980). Pre-existing (aerobic) protein synthesis is repressed while selective synthesis of new polypeptides is initiated (Sachs et al., 1980). This is most likely a plant s natural response to flooding. 

The induction of anaerobic treatment synthesis occurs in two phases. During the first few hours of anaerobic treatment there is a transition period during which there is a rapid increase in the synthesis of a class of polypeptides with an approximate molecular weight of 33 kDa (Fig. 3). These have, been referred to as the transition polypeptides (TPs) as they represent most of the protein synthesis occurring in early anaerobiosis. 

Fig. 3. Protein synthesis in a maize primary root during ( ) one hr pulse labelling with [ HJleucine under aerobic conditions (b)-(e) pulse labelling with [ HJIeucine during the specified times under anaerobic conditions. The arrow labelled TPs indicates the position of the transition polypeptides. The unlabelled arrow indicates the position of alcohol dehydrogenase 1 (ADHl). From Sachs et al. (1980).

In the presence of air, the roots, coleoptile, mesocotyl, endosperm, scutellum, and anther wall of maize synthesise a tissue-specific spectrum of polypeptides. The scutellum and endosperm of the immature kernel synthesise many or all of the ANPs constitutively, along with many other proteins under aerobic conditions. Under anaerobic conditions all of the above organs selectively synthesise only the ANPs. Moreover, except for a few characteristic qualitative and quantitative differences, the patterns of anaerobic protein synthesis in these diverse organs are remarkably similar (Okimoto et al., 1980). On the other hand, maize leaves, which have emerged from the coleoptile, do not incorporate labelled amino acids under anaerobic conditions and do not survive even a brief exposure to anaerobiosis (Okimoto et al., 1980). 

Bacitracin and gramicidin are polypeptide antibiotics with activity against gram-positive organisms and against most anaerobic cocci. Systemic toxicity for bacitracin is rare because of poor absorption through the skin. Gramicidin is used only topically... 

The [2Fe 2S], [3Fe S], and [4Fe S] clusters that are found in simple Fe S proteins are also constituents of respiratory and photosynthetic electron transport chains. Multicluster Fe S enzymes such as hydrogenase, formate dehydrogenase, NADH dehydrogenase, and succinate dehydrogenase feed electrons into respiratory chains, while others such as nitrate reductase, fhmarate reductase, DMSO reductase, and HDR catalyze the terminal step in anaerobic electron transport chains that utihze nitrate, fumarate, DMSO, and the CoB S S CoM heterodisulfide as the respiratory oxidant. All comprise membrane anchor polypeptide(s) and soluble subunits on the membrane surface that mediate electron transfer to or from Mo cofactor (Moco), NiFe, Fe-S cluster or flavin active sites. Multiple Fe-S clusters define electron transport pathways between the active site and the electron donor or... 

Fig. 12.6. The onset of synthesis of various mitochondrial polypeptides upon transferring anaerobically grown yeast cells to aerobic conditions. Yeast cells were grown overnight under anaerobic conditions. At time zero they were transferred to aerobic conditions, and at the indicated time periods samples of cells were removed and lysed in the presence of NaOH and mercaptoethanol. Samples containing about 50 /ig of protein were electrophoresed in a sodium dodecyl sulfate-polyacrylamide gel. The proteins were electrotransferred to nitrocellulose sheets and decorated with specific antibodies and l-labelled protein A. Paper pieces corresponding to the labelled protein spots were cut out from the immune blot and counted in a y counter. The amount of counts obtained in the samples of 8 h aerobic conditions was taken as 100%. The antibodies used were directed against the following polypeptides porin of the mitochondrial outer membrane (29 k) /8 subunit of the proton-ATPase (iS-F,) subunit IV of cytochrome c oxidase (OxIV) and subunit V of cytochrome c oxidase (OxV).

The 1-Fe rubredoxins are single polypeptide chain proteins of about 55 amino acid residues and 6,000 dalton molecular weight. The primary structure of the Microccus aerogenes (220, 221) and Peptostreptoccus elsdenii (210) proteins have been determined. The two amino acid sequences (Fig. 11) reveal a relatively high mutation frequency, with a noticeable conservancy around the four cysteinyl residues which are critically involved in binding the iron and hence in the proposed electron transfer role of the protein (210). Another curious feature of the anaerobic rubredoxins is the presence of N-formyl methionine as N-terminus amino acid (222). Synthesis of the polypeptide is in progress (223). 

An NADH-flavin oxidoreductase was also induced by cholic acid in this bacterium [61]. The physiological function of this enzyme in 7-dehydroxylation is presently unknown. Moreover, it is not known which of the induced polypeptides constitute 7-dehydroxylase however, the polypeptides of 56 000 and 27 000 molecular weight co-purify with enzymatic activity upon anaerobic high-performance gel filtration. 

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