title: High-level secretion of a chimeric thermostable lichenase from Bacillus subtilis by screening of site-mutated signal peptides with structural alterations.
abstract: A chimeric gene mHG (669 bp) was constructed by substitution of Clostridium thermocellum ZJL4 lichenase (CG) N-terminal fragment (except its signal sequence) for the counterpart of Bacillus sp. A3 lichenase (BG). To acquire high-level secretion of the chimeric lichenase (mHG) in Bacillus subtilis, a series of site-mutated signal peptides were designed. The activity of mHG, which was directed by an artificial hydrophobic signal peptide H1 (MMARKIAGMATSLLVIFSSSAVA) from cytoplasm into growth medium, reached 80.56 U/ml after 22-h incubation, indicating that signal peptide hydrophobicity appears to be critical for early stages in mHG export. By purification of the mHG (approximately 25.3 kDa) from cultures of B. subtilis (pBSG-H1), enzymatic property assays showed that the common optima for mHG were 70 degrees C and pH 5.0. The residual activity of mHG at 90 degrees C for 10 min was 83.45% of its maximum activity, which was almost similar to that of CG (90 degrees C, 10 min, 84.33%). This constructed shuttle expression vector with a novel signal peptide exhibited its applicability for high-level production of heterologous proteins from B. subtilis. Moreover, the high-level secreted mHG with relatively high thermostability could be a potential candidate for feed industrial applications.
authors.affiliation: Key Laboratory of Molecular Animal Nutrition, Ministry of Education, College of Animal Sciences, Zhejiang University, Hangzhou 310029, China.
authors.forename: Ling-lin
authors.initials: LL
authors.lastname: Fu
authors.forename: Zi-rong
authors.initials: ZR
authors.lastname: Xu
authors.forename: Jiang-bing
authors.initials: JB
authors.lastname: Shuai
authors.forename: Chun-xia
authors.initials: CX
authors.lastname: Hu
authors.forename: Wei
authors.initials: W
authors.lastname: Dai
authors.forename: Wei-fen
authors.initials: WF
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D001709:Biotechnology / Q000379:methods; D048013:Acetivibrio thermocellus / Q000201:enzymology / Q000235:genetics; D004795:Enzyme Stability; D006026:Glycoside Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006358:Hot Temperature; D008969:Molecular Sequence Data; D009154:Mutation; D021382:Protein Sorting Signals / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D006026:Glycoside Hydrolases; C028020:licheninase