Characterization of key proteins involved in the SCB signalling system for secondary metabolism in Streptomyces coelicolor

γ-Butyrolactones are bacterial hormones mainly produced by Streptomyces and have an important role in cellular physiology which includes the regulation of secondary metabolite (i.e. antibiotics) production and, in some cases, morphological development. The γ-butyrolactones bind to their cognate binding proteins which are often repressors, resulting in transcription derepression of γ-butyrolactone binding protein target genes and eventually leading to the production of antibiotics and/or morphological development.
In this thesis, two γ-butyrolactones (SCB2 and SCB3) produced by Streptomyces coelicolor were isolated and characterized. Similar to the previously identified γ-butyrolactone, SCB1, both were shown to have the ability to induce antibiotic production and to bind to ScbR, the γ-butyrolactone receptor. The binding affinities of ScbR to these three γ-butyrolactones and their analogues were analyzed by a newly developed γ-butyrolactone detection method. The results suggest that ScbR has a high affinity toward γ-butyrolactones with a long C2 side chain, a C1’-β-hydroxyl group and a C6’-methyl group (e.g. SCBs).
Introduction of point mutations in the predicted active sites of ScbA via site-directed mutagenesis led to a loss of SCB production in the host strain. This suggests that ScbA has an enzymatic function in the synthesis of the γ-butyrolactones. These ScbA point mutants also showed different phenotypes in antibiotic production and sporulation, implying an additional regulatory role of ScbA. Further detailed investigations of these potential regulatory functions or enzymatic activities of ScbA are needed in order to reveal the actual roles of ScbA in the physiology of S. coelicolor.

	Titel
	Hoofdstuk 1
	Hoofdstuk 2
	Hoofdstuk 3
	Hoofdstuk 4 (Embargo t/m 27 november 2012)
	Hoofdstuk 5 (Embargo t/m 27 november 2012)
	Hoofdstuk 6 (Embargo t/m 27 november 2012)
	Samenvatting
	Bibliografie
	Appendix
	Volledige dissertatie (Embargo t/m 27 november 2012)

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