title: Magnesium ions increase the activity of Bacillus deramificans pullulanase expressed by Brevibacillus choshinensis.
abstract: Addition of MgCl2 to the culture medium has been found to dramatically increase the activity of Bacillus deramificans pullulanase expressed by Brevibacillus choshinensis. The specific activity of the pullulanase obtained from medium supplemented with MgCl2 was also higher than that obtained in culture medium without added magnesium ions. In this work, the mechanism of this increase was studied. When cultured in medium without added magnesium ions, B. choshinensis mainly produced a thermolabile, inactive form of pullulanase. The addition of magnesium ions led to the production of a thermostable, active form of pullulanase. Circular dichroism assays revealed considerable differences in secondary structure between the active and inactive pullulanase forms. Transmission electron microscopy suggested that magnesium ion addition inhibits the shedding of cell wall protein (HWP) layers from the cell surface. Quantitative real-time PCR showed that magnesium ion addition represses transcription of HWP. Because the pullulanase gene and HWP have identical promoters, pullulanase gene transcription was also inhibited. These results suggest that when pullulanase is expressed slowly, it tends to fold into an active form.
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China.|School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China.
authors.forename: Chun
authors.initials: C
authors.lastname: Zou
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China.|School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China.
authors.forename: Xuguo
authors.initials: X
authors.lastname: Duan
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China. jingwu@jiangnan.edu.cn.|School of Biotechnology and Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China. jingwu@jiangnan.edu.cn.
authors.forename: Jing
authors.initials: J
authors.lastname: Wu
mesh_terms: D001407:Bacillus / Q000201:enzymology* / Q000235:genetics*; D058675:Brevibacillus / Q000235:genetics / Q000378:metabolism*; D002473:Cell Wall / Q000378:metabolism* / Q000648:ultrastructure; D002942:Circular Dichroism; D006026:Glycoside Hydrolases / Q000378:metabolism*; D015636:Magnesium Chloride / Q000494:pharmacology*; D046529:Microscopy, Electron, Transmission; D011401:Promoter Regions, Genetic / Q000235:genetics; D017510:Protein Folding; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D015636:Magnesium Chloride; D006026:Glycoside Hydrolases; C100181:pullulanase
keywords: Active form; Brevibacillus choshinensis; Cell wall protein; Magnesium ions; Pullulanase