Catabolite repression by glucose 6‐phosphate, gluconate and lactose in Escherichia coli
| Autor: | Boris M. Hogema, Karel Van Dam, Hiroji Aiba, Jos C. Arents, Pieter W. Postma, Toshifumi Inada |
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| Rok vydání: | 1997 |
| Předmět: |
Catabolite repression
Glucose-6-Phosphate lac operon Lactose Gluconates Microbiology Receptors Cyclic AMP chemistry.chemical_compound Cyclic AMP Escherichia coli Phosphoenolpyruvate Sugar Phosphotransferase System Molecular Biology Psychological repression biology Gene Expression Regulation Bacterial PEP group translocation Carbon Fed-batch culture Glucose 6-phosphate chemistry Biochemistry cAMP receptor protein biology.protein Adenylyl Cyclases |
| Zdroj: | Molecular Microbiology. 24:857-867 |
| ISSN: | 1365-2958 0950-382X |
| DOI: | 10.1046/j.1365-2958.1997.3991761.x |
| Popis: | Summary While catabolite repression by glucose has been studied extensively and is understood in large detail in Enterobacteriaceae, catabolite repression by carbohydrates that are not transported by the phosphotransferase system (PTS) has always remained an enigma. Examples of non-PTS carbohydrates that cause catabolite repression in Escherichia coli are gluconate, lactose and glucose 6-phosphate. In this article it is shown that enzyme IIA Glc of the PTS is not involved in catabolite repression by these carbon sources. Carbon sources that caused strong catabolite repression of b-galactosidase lowered the concentration of both cAMP and the cAMP receptor protein (CRP). A strong correlation was found between the amounts of cAMP and CRP and the strength of the repression. The levels of cAMP and CRP were modulated in various ways. Neither overproduction of CRP nor an increased cAMP concentration could completely relieve the repression by glucose 6-phosphate, lactose and gluconate. Simultaneously increasing the cAMP and the CRP levels was lethal for the cells. In a mutant expressing a constant amount of cAMP-independent CRP *protein, catabolite repression was absent. The same was found in a mutant in which lac transcription is independent of cAMP/CRP. These results, combined with the fact that both the cAMP and the CRP levels are lowered by glucose 6-phosphate, lactose and gluconate, lead to the conclusion that the decreased cAMP and CRP levels are the cause of catabolite repression by these nonPTS carbon sources. |
| Databáze: | OpenAIRE |
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