Cloning and molecular characterization of csm mutations allowing expression of catabolite-repressible operons in the absence of exogenous cyclic AMP

Methylglyoxal in living organisms: chemistry, biochemistry, toxicology and biological implications

Despite the growing interest towards methylglyoxal and glyoxalases their real role in metabolic network is still obscure. In the light of developments several reviews have been published in this field mainly dealing with only a narrow segment of this research area. In this article a trial is made to present a comprehensive overview of methylglyoxal research, extending discussion from chemistry to biological implications by reviewing some important characteristics of methylglyoxal metabolism and toxicity in a wide variety of species, and emphasizing the action of methylglyoxal on energy production, free radical generation and cell killing. Special attention is paid to the discussion of alpha-oxoaldehyde production in the environment as a potential risk factor and to the possible role of this a-dicarbonyl in diseases. Concerning the interaction of methylglyoxal with biological macromolecules (DNA, RNA, proteins) an earlier review (Kalapos, Toxicology Letters, 73, 1994, 3-24) means a supplementation to this paper, thus hoping the avoidance of unnecessary bombast. The paper arrives at the conclusion that since the early stage of evolution the function of methylglyoxalase pathway has been related to carbohydrate metabolism, but its significance has been changed over the thousands of years. Namely, at the beginning of evolution methylglyoxalase path was essential for the reductive citric acid cycle as an anaplerotic route, while in the extant metabolism it concerns with the detoxification of methylglyoxal and plays some regulatory role in triose-phosphate household. As there is a tight junction between methylglyoxal and carbohydrate metabolism its pathological role in the events of the development of diabetic complications emerges in a natural manner and further progress is hoped in this field. In contrast, significant advancement cannot be expected in relation to cancer research.

Linkage map of Escherichia coli K-12, edition 10: the traditional map

This map is an update of the edition 9 map by Berlyn et al. (M. K. B. Berlyn, K. B. Low, and K. E. Rudd, p. 1715-1902, in F. C. Neidhardt et al., ed., Escherichia coli and Salmonella: cellular and molecular biology, 2nd ed., vol. 2, 1996). It uses coordinates established by the completed sequence, expressed as 100 minutes for the entire circular map, and adds new genes discovered and established since 1996 and eliminates those shown to correspond to other known genes. The latter are included as synonyms. An alphabetical list of genes showing map location, synonyms, the protein or RNA product of the gene, phenotypes of mutants, and reference citations is provided. In addition to genes known to correspond to gene sequences, other genes, often older, that are described by phenotype and older mapping techniques and that have not been correlated with sequences are included.

Cyclic AMP in prokaryotes

Cyclic AMP (cAMP) is found in a variety of prokaryotes including both eubacteria and archaebacteria. cAMP plays a role in regulating gene expression, not only for the classic inducible catabolic operons, but also for other categories. In the enteric coliforms, the effects of cAMP on gene expression are mediated through its interaction with and allosteric modification of a cAMP-binding protein (CRP). The CRP-cAMP complex subsequently binds specific DNA sequences and either activates or inhibits transcription depending upon the positioning of the complex relative to the promoter. Enteric coliforms have provided a model to explore the mechanisms involved in controlling adenylate cyclase activity, in regulating adenylate cyclase synthesis, and in performing detailed examinations of CRP-cAMP complex-regulated gene expression. This review summarizes recent work focused on elucidating the molecular mechanisms of CRP-cAMP complex-mediated processes. For other bacteria, less detail is known. cAMP has been implicated in regulating antibiotic production, phototrophic growth, and pathogenesis. A role for cAMP has been suggested in nitrogen fixation. Often the only data that support cAMP involvement in these processes includes cAMP measurement, detection of the enzymes involved in cAMP metabolism, or observed effects of high concentrations of the nucleotide on cell growth.

Cyclic AMP in prokaryotes

Cyclic AMP (cAMP) is found in a variety of prokaryotes including both eubacteria and archaebacteria. cAMP plays a role in regulating gene expression, not only for the classic inducible catabolic operons, but also for other categories. In the enteric coliforms, the effects of cAMP on gene expression are mediated through its interaction with and allosteric modification of a cAMP-binding protein (CRP). The CRP-cAMP complex subsequently binds specific DNA sequences and either activates or inhibits transcription depending upon the positioning of the complex relative to the promoter. Enteric coliforms have provided a model to explore the mechanisms involved in controlling adenylate cyclase activity, in regulating adenylate cyclase synthesis, and in performing detailed examinations of CRP-cAMP complex-regulated gene expression. This review summarizes recent work focused on elucidating the molecular mechanisms of CRP-cAMP complex-mediated processes. For other bacteria, less detail is known. cAMP has been implicated in regulating antibiotic production, phototrophic growth, and pathogenesis. A role for cAMP has been suggested in nitrogen fixation. Often the only data that support cAMP involvement in these processes includes cAMP measurement, detection of the enzymes involved in cAMP metabolism, or observed effects of high concentrations of the nucleotide on cell growth.

Generation of deletions in the 3'-flanking sequences of the Escherichia coli crp gene that induce cyclic AMP suppressor functions

The crp structural gene and its 3'-flanking sequences were subcloned into M13mp8, and in vitro deletions were constructed in both the 5' and 3' ends of the gene by using Bal 31 nuclease. Deletions ranged in size from 24 to 250 base pairs at the 5' end of crp. Sixteen deletions generated at the 3' end of the gene ranged in size from 133 to 675 base pairs. The majority of deletions extended into the crp structural gene. Another class of deletions, i.e., delta crp-4, delta crp-17, and delta crp-2, had endpoints extending in the 3'-flanking sequences external to the crp structural gene. Deletions were subcloned into pBR322 and transformed into the Escherichia coli cya crp deletion strain NCR438. Transformants containing plasmid pBM4 with the delta crp4 mutation, a deletion of 133 base pairs, were cyclic AMP independent. Strain NCR440 harboring this plasmid expressed beta-galactosidase and threonine dehydratase activities and fermented lactose, ribose, arabinose, and xylose in the absence of exogenous cyclic AMP. The delta crp-4 mutation also caused strain NCR440 to be hypersensitive to exogenous cyclic AMP. The cylic AMP receptor protein expressed in maxicells from pBM4 carrying the delta crp-4 mutation comigrated with the wild-type protein on electrophoretic gels. The delta crp-4 mutation demonstrates that sequences distal to the crp structural gene can mediate cyclic AMP suppressor functions.

Deletion of a repetitive extragenic palindromic (REP) sequence downstream from the structural gene of Escherichia coli glutamate dehydrogenase affects the stability of its mRNA

A deletion that removes one repetitive extragenic palindromic sequence downstream of the structural gene of Escherichia coli glutamate dehydrogenase, reduces twofold the half-life of gdhA mRNA.