Mechanismen der Regulation des pca-qui-Operons aus dem Bakterium Acinetobacter baylyi Stamm ADP1
Schrade, Betina Wilma
FacultiesFakultät für Naturwissenschaften
LicenseStandard (Fassung vom 01.10.2008)
Acinetobacter baylyi is able to utilize aromatic compounds via the ß-ketoadipate-pathway which consists of two branches. This study focusses on the protocatechuate branch whose enzymes are encoded by the pca genes. The regulation of gene expression was analyzed with regard to the different levels of regulation in the intergenic region between pcaU and pcaI. Using a reportergene system in E. coli it was shown that the PcaU induction with protocatechuate is not specific. Some phenols and anilines affected an induction. The influence of additional aromatic compounds on the PcaU induction by protocatechuate was 80 to 99 % of the induction caused by protocatechuate only. The CatM and BenM bindingside in the nontranslated region of pcaU was confirmed by a mutation and by gelretardation assays. No more bonding of BenM-6His occured. Due to this mutation the expression of the structure genes was completely prevented. Mutations created in the 5’-nontranslated region of pcaI were analysed. All of these mutations caused an elimination of the structurgene expression. An influence of the mutations in this region on the crossregulation was excluded. Reportergene studies showed that changes in distance between the PcaU bindingsite and the promoter of the structure genes on the chromosome of Acinetobacter nearly eliminated the expression if the angle of binding between the protein bindingsites on the DNA changed differently than 180 or 360°. Reportergene studies showed that mutations in the distance between PcaU binding site and structure gene promoter didn’t have any influence under crossregulation conditions. Highly conserved guanine nucleotides in the PcaU bindingsite, could be confirmed in this work. By performing reportergene studies with mutants that have been changed in these Guanine nucleotides a nearly absolute elimination of structuregene expression was found. Gelretardation assays of the mutants showed a partly reduced binding affinity.
Subject HeadingsAcinetobacter [GND]
Aromatic compounds [LCSH]