Carbon Catabolite Repression and the Related Genes of ccpA, ptsH and hprK in Thermoanaerobacterium aotearoenseReport as inadecuate




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The strictly anaerobic, Gram-positive bacterium, Thermoanaerobacterium aotearoense SCUT27, is capable of producing ethanol, hydrogen and lactic acid by directly fermenting glucan, xylan and various lignocellulosically derived sugars. By using non-metabolizable and metabolizable sugars as substrates, we found that cellobiose, galactose, arabinose and starch utilization was strongly inhibited by the existence of 2-deoxyglucose 2-DG. However, the xylose and mannose consumptions were not markedly affected by 2-DG at the concentration of one-tenth of the metabolizable sugar. Accordingly, T. aotearoense SCUT27 could consume xylose and mannose in the presence of glucose. The carbon catabolite repression CCR related genes, ccpA, ptsH and hprK were confirmed to exist in T. aotearoense SCUT27 through gene cloning and protein characterization. The highly purified Histidine-containing Protein HPr could be specifically phosphorylated at Serine 46 by HPr kinase-phosphatase HPrK-P with no need to add fructose-1,6-bisphosphate FBP or glucose-6-phosphate Glc-6-P in the reaction mixture. The specific protein-interaction of catabolite control protein A CcpA and phosphorylated HPr was proved via affinity chromatography in the absence of formaldehyde. The equilibrium binding constant KD of CcpA and HPrSerP was determined as 2.22 ± 0.36 nM by surface plasmon resonance SPR analysis, indicating the high affinity between these two proteins.



Author: Muzi Zhu, Yanping Lu, Jufang Wang, Shuang Li , Xiaoning Wang

Source: http://plos.srce.hr/



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