Escherichia coli initiation

Although AUG is the initiation codon normally used in bacteria, studies of binding of fMet-tRNAf to ribosomes (Clarck and Marcher, 1966) or translation of synthetic polynucleotides (Thach et ai, 1966) have revealed that GUG and, to a lesser extent, UUG are also functional initiation codons. A single case of initiation at an AUU codon is also known for the Escherichia coli initiation factor IF-3 protein (Sacerdot et ai, 1982). By contrast, a compilation of over 200 ribosome binding site sequences in eukaryotic mRNA (Kozak, 1981a, 1983) has yielded only AUG as initiation codon. It appears, therefore, that initiation of eukaryotic translation occurs exclusively at AUG codons. 

A strain of Escherichia coli produces a naphthotriazole from 2,3-diaminonaphthalene and nitrite that is formed from nitrate by the action of nitrate reductase. The initial product is NO, which is converted by reactions with oxygen into the active nitrosylating agent that reacts chemically with the amine (Ji and Hollocher 1988). A comparable reaction may plausibly account for the formation of dimethylnitrosamine by Pseudomonas stutzeri during growth with dimethylamine in the presence of nitrite (Mills and Alexander 1976) (Figure 2.2f). 

Diaz E, A Ferrandez, JL Garcia (1998) Characterization of the hca cluster encoding the dioxygenolytic pathway for initial catabolism of 3-phenylpropionic acid in Escherichia coli K-12. J Bacterial 180 2915-2923. 

Edery, I., Altmann, M., and Sonenberg, N. (1988). High-level synthesis in Escherichia coli of functional cap-binding eukaryotic initiation factor eIF-4E and affinity purification using a simplified cap-analog resin. Gene 74, 517-525. 

The first report on the anticancer properties of ruthenium was published in 1976 when the Ru(III) compound /ac-[RuC13(NH3)3] (Fig. 11) was found to induce filamentous growth of Escherichia coli at concentrations comparable to those at which cisplatin generates similar effects (49). This Ru(III) complex and related compounds such as cis-[RuCl2(NH3)4]Cl illustrated the potential anticancer activity of ruthenium complexes, but insolubility prevented further pharmacological use. Since these initial studies, other Ru(III) complexes have been studied for potential anticancer activity, and two compounds, NAMI-A (50) and KP1019 (51), are currently undergoing clinical trials. Remarkably,... 

Detection of one molecule of P-D-galactosidase produced from Escherichia coli 152 Bovine serum albumin increases initial light intensity and eliminates the ad- 153... 

Cervera and Levine [81] studied the mechanism of oxidative modification of glutamine synthetase from Escherichia coli. It was found that active oxygen species initially caused inactivation of the enzyme and generated a more hydrophilic protein, which still was not a substrate for the protease. Continuous action of oxygen species resulted in the formation of oxidized protein subjected to the proteolytic attack of protease. 

The reaction catalyzed by KDO 8-phosphate synthetase (reaction 2, Scheme 35) was first observed by Levin and Racker9 in extracts from Pseudomonas aeruginosa (see Scheme 1), and later by Ghalambor and Heath29 in extracts from Escherichia coli 0111 B4 and J-5. In the initial experiments of Levin and Racker,135 the fate of D-ribose 5-phosphate in crude bacterial extracts was studied, and the KDO 8-phosphate discovered by the authors is really derived from D-ribose 5-phosphate by three, sequential, enzyme-catalyzed reactions (see Scheme 36). 

The initial procedures involved in expression of the Rhodnius nitrophorins in Escherichia coli were worked out for NPl by Drs. Donald E. Champagne and John F. Andersen at the University of Arizona during the spring and summer of 1996, and the purification protocols were... 

Several methods for performing the test have been described, the guideline describes the diffusion and suspension test. Bacteria should be exposed to the test substance both in the presence and absence of an appropriate metabolic activation system. The response is expressed in the preferential inhibition of growth or the preferential killing of the DNA repair deficient strain. Escherichia coli polA (W3110/p3478) or Bacillus subtilis rec (H17/M45) pairs are recommended. The test should initially be performed over a broad range of concentrations. 

The test is commonly employed as an initial screen for genotoxic activity and, in particular, for point mutation-inducing activity. It detects point mutations, which involve substimtion, addition or deletion of one or a few DNA base pairs. The reverse mutation test in either Salmonella typhimurium or Escherichia coli detects mutation in an amino acid requiring strain (histidine or tryptophan, respectively) to produce a strain independent of an outside supply of amino acid. The principle of the test is that it detects mutations, which revert mutations present in the test strains and restore the functional capability of the bacteria to synthesize an essential amino acid. The revertant bacteria are detected by their ability to grow in the absence of the amino acid required by the parent test strain. 

Initial rate patterns for Escherichia coli NAD+-dependent coenzyme A-linked aldehyde dehydrogenase (Reaction NAD+ + CoA-SFI + acetaldehyde = NADFI + acetyl-S-CoA + FI+). The results of each of three experiments are shown as a single double-reciprocal plot, and the nonvaried substrate concentrations for each curve are indicated above the data points. 

Figure 2. Illustration of the importance of the choice of reaction conditions on the determination of initial velocity. Shown are four conditions applied to examine the rate behavior of Escherichia coli NAD+-dependent coenzyme A-linked aldehyde dehydrogenase (Reaction NAD+ + CoA-SH + Acetaldehyde = NADH + Acetyl-S-CoA + H+). All assay mixtures contained enzyme, 0.5 mM NAD+, 8 /jlW CoA-SFI, 16 mM acetaldehyde, and 22.5 mM Tris buffer at pFI 8.1. (a) Time-course observed when enzyme was added to the standard assay (b) time-course observed when enzyme was added to standard assay augmented with 10 mM 2-mercaptoethanol (c) time-course observed when enzyme was first preincubated for 15 min with 8 /jlW CoA-SH, 16 mM acetaldehyde, 10 mM 2-mercaptoethanol, and 22.5 mM Tris buffer at pH 8.1, and the reaction was initiated by addition of NAD+ (d) time-course observed when enzyme was preincubated with lOmM 2-mercaptoethanol for 15 min andthen addedtostandard assay augmented with 10 mM 2-mercaptoethanol. The data are most compatible with the idea that the enzyme has an active-site thiol group that must be reduced to express full catalytic activity during assay.

---