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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 209 (2002), S. 0 
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Carbon catabolite repression (CCR) in bacteria is generally regarded as a regulatory mechanism to ensure sequential utilization of carbohydrates. Selection of the carbon sources is mainly made at the level of carbohydrate-specific induction. Since virtually all carbohydrate catabolic genes or operons are regulated by specific control proteins and require inducers for high level expression, direct control of the activity of regulators or control of inducer formation is an efficient measure to keep them silent. By these mechanisms, bacteria are able to establish a hierarchy of sugar utilization. In addition to the control of induction processes by CCR, bacteria have developed global transcriptional regulation circuits, in which pleiotropic regulators are activated. These global control proteins, the catabolite gene activator protein (CAP), also known as cAMP receptor protein, in Escherichia coli or the catabolite control protein (CcpA) in Gram-positive bacteria with low GC content, act upon a large number of catabolic genes/operons. Since practically any carbon source is able to trigger global transcriptional control, expression of sugar utilization genes is restricted even in the sole presence of their cognate substrates. Consequently, CAP- or CcpA-dependent catabolite repression serves as an autoregulatory device to keep sugar utilization at a certain level rather than to establish preferential utilization of certain carbon sources. Together with other autoregulatory mechanisms that are not acting at the gene expression level, CCR helps bacteria to adjust sugar utilization to their metabolic capacities. Therefore, catabolic/metabolic balance would perhaps better describe the physiological role of this regulatory network than the term catabolite repression.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We provide a functional and regulatory analysis of glcP, encoding the major glucose transporter of Streptomyces coelicolor A3(2). GlcP, a member of the Major Facilitator Superfamily (MFS) of bacterial and eucaryotic sugar permeases, was found to be encoded twice at two distinct loci, glcP1 and glcP2, located in the central core and in the variable right arm of the chromosome respectively. Heterologous expression of GlcP in Escherichia coli led to the full restoration of glucose fermentation to mutants lacking glucose transport activity. Biochemical analysis revealed an affinity constant in the low-micromolar range and substrate specificity for glucose and 2-deoxyglucose. Deletion of glcP1 but not glcP2 led to a drastic reduction in growth on glucose reflected by the loss of glucose uptake. This correlated with transcriptional analyses, which showed that glcP1 transcription was strongly inducible by glucose, while glcP2 transcripts were barely detectable. In conclusion, GlcP, which is the first glucose permease from high G+C Gram-positive bacteria characterized at the molecular level, represents the major glucose uptake system in S. coelicolor A3(2) that is indispensable for the high growth rate on glucose. It is anticipated that the activity of GlcP is linked to other glucose-mediated phenomena such as carbon catabolite repression, morphogenesis and antibiotic production.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1572-9699
    Keywords: carbon catabolite repression ; glucose kinase ; Streptomyces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glucose kinase of Streptomyces coelicolor A3(2) is essential for glucose utilisation and is required for carbon catabolite repression (CCR) exerted through glucose and other carbon sources. The protein belongs to the ROK-family, which comprises bacterial sugar kinases and regulators. To better understand glucose kinase function, we have monitored the cellular activity and demonstrated that the choice of carbon sources did not significantly change the synthesis and activity of the enzyme. The DNA sequence of the Streptomyces lividans glucose kinase gene glkA was determined. The predicted gene product of 317 amino acids was found to be identical to S. coelicolor glucose kinase, suggesting a similar role for this protein in both organisms. A procedure was developed to produce pure histidine-tagged glucose kinase with a yield of approximately 10 mg/l culture. The protein was stable for several weeks and was used to raise polyclonal antibodies. Purified glucose kinase was used to explore protein-protein interaction by surface plasmon resonance. The experiments revealed the existence of a binding activity present in S. coelicolor cell extracts. This indicated that glucose kinase may interact with (an)other factor(s), most likely of protein nature. A possible cross-talk with proteins of the phosphotransferase system, which are involved in carbon catabolite repression in other bacteria, was investigated.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1572-9699
    Keywords: PTS ; phosphotransferase system ; sugar transport ; Streptomyces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Our research group is studying the phosphotransferase system (PTS) of Streptomyces coelicolor, which, in other bacteria, is centrally involved in carbon source uptake and regulation. We have surveyed the public available S. coelicolor genome sequence produced by the ongoing genome sequencing project for pts gene homologues (http://www.sanger.ac.uk/Projects/S_coelicolor/). Three genes encoding homologues of the general PTS components enzyme I (ptsI), HPr (ptsH), and enzyme IIACrr (crr; IIAGlc-homologue) and six genes encoding homologues of sugar-specific PTS components were identified. The deduced primary sequences of the sugar-specific components shared significant similarities to PTS permeases of the mannitol/fructose family and of the glucose/sucrose family. A model is presented, in which possible functions of the novel described PTS homologues are discussed.
    Type of Medium: Electronic Resource
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