Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Escherichia coli cells grown anaerobically in the presence of nitrate reduce the nitrate as a terminal electron acceptor in place of molecular oxygen by an induced respiratory-type electron transferring system residing in the inner membrane structure. When oxygen is introduced to a suspension of nitrate-respiring cells, the oxygen is immediately reduced preferentially and the cellular uptake of nitrate ceases abruptly. In contrast, we found that the cells exhibited no oxygen control on uptake of chlorate, a competitive substrate analogue, indicating operation of an oxygen-sensitive transport system specific to nitrate. This was further evidenced by the fact that chlorate inhibition of reduction of nitrate was brought about only when the transport of both chlorate and nitrate was facilitated by the aid of carrier-type chlorate (or nitrate) ionophore. We demonstrated that oxygen inhibition on reduction of nitrate was abolished within the cells treated by octyl glucoside resulting in a removal of permeability barrier specific to nitrate. We conclude that the transient control by molecular oxygen is primarily due to the inhibition of nitrate transport into the cytoplasmic side. Since nitrate induces the nitrate-respiring system, the repression of the nitrate reductase operon by molecular oxygen is consistently interpreted on the basis of the "inducer exclusion mechanism."
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PMID:Molecular oxygen controls nitrate transport of Escherichia coli nitrate-respiring cells. 329 57

Four detergents (octyl glucoside, zwittergent, Triton X-100, and Nonidet P-40) were examined with regard to their efficiency in solubilizing and retaining the activity of the nitrate reductase of Bacillus stearothermophilus. At a concentration of between 0.4 and 0.6%, the non-ionic detergent octyl glucoside solubilized only 64% of the membrane proteins. However, about 100% of the nitrate reductase activity was recovered in the soluble fraction. In contrast, the zwitterionic detergent 3-(alkyldimethylammonio)-1-propanesulphonate (3-16) solubilized 100% of the membrane proteins, but only 77% of the nitrate reductase activity was recovered. Two other non-ionic detergents, Triton X-100 and Nonidet P-40 also solubilized 100% of the membrane proteins, but there was a dramatic increase in total enzyme activity following solubilization. The enzyme activity was not stable in any of the four detergents for more than 2 days. Nevertheless, octyl glucoside was preferred because of the additional advantage of ammonium sulphate fractionation.
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PMID:Detergent solubilization of the respiratory nitrate reductase of Bacillus stearothermophilus. 378 23

Hydrophobic membrane proteins often have complex functions and are thus of great interest. However, their analysis presents a challenge because they are not readily soluble in polar solvents and often undergo aggregation. We present a sequential CNBr and trypsin in-gel digestion method combined with mass spectrometry for membrane protein analysis. CNBr selectively cleaves methionine residues. But due to the low number of methionines in proteins, CNBr cleavage produces a small number of large peptide fragments with MWs typically >2000, which are difficult to extract from gel pieces. To produce a larger number of smaller peptides than that obtained by using CNBr alone, we demonstrate that trypsin can be used to further digest the sample in gel. The use of n-octyl glucoside (n-OG) to enhance the digestion efficiency and peptide recovery was also studied. We demonstrate that the sensitivity of this membrane protein identification method is in the tens of picomole regime, which is compatible to the Coomassie staining gel-spot visualization method, and is more sensitive than other techniques reported in the literature. This CNBr/trypsin in-gel digestion method is also found to be very reproducible and has been successfully applied for the analysis of complex protein mixtures extracted from biological samples. The results are presented from a study of the analysis of bacteriorhodopsin, nitrate reductase 1 gamma chain, and a complex protein mixture extracted from the endoplasmic recticulum membrane of mouse liver.
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PMID:Development and applications of in-gel CNBr/tryptic digestion combined with mass spectrometry for the analysis of membrane proteins. 1458 51