title: Five mutations in N-terminus confer thermostability on mesophilic xylanase.
abstract: The termini of a pair of xylanases, one of mesophilic and one of thermophilic origin, was studied by molecular dissection and systematic mutagenesis. The thermostability of the mesophilic xylanase SoxB from Streptomyces olivaceovirdis was significantly improved by substituting its 33 N-terminal amino acid residues with the corresponding residues of the thermophilic xylanase TfxA from Thermomonospora fusca. Five amino acid substitutions, which clustered in one of the regions of the N-terminus, were discovered, for the first time, to account for the majority of the improvement in thermostability of SoxB. Further systematic mutagenesis and analysis of the five mutations demonstrated that comprehensive synergism of the five mutations was involved in conferring the thermostability on the SoxB. Moreover, when the five thermostabilizing mutations were introduced into two other G/11 xylanases, SlxB from Streptomyces lividans and AnxB from Aspergillus niger, their thermostabilities were also dramatically enhanced.
authors.affiliation: Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China.
authors.forename: Shan
authors.initials: S
authors.lastname: Zhang
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Xiuzhen
authors.initials: X
authors.lastname: Chen
authors.forename: Xin
authors.initials: X
authors.lastname: Chu
authors.forename: Fei
authors.initials: F
authors.lastname: Sun
authors.forename: Zhiyang
authors.initials: Z
authors.lastname: Dong
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D043364:Endo-1,4-beta Xylanases / Q000737:chemistry* / Q000235:genetics; D004795:Enzyme Stability / Q000235:genetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D013302:Streptomyces / Q000201:enzymology*; D001617:beta-Glucosidase / Q000737:chemistry* / Q000235:genetics
chemical_list: D011993:Recombinant Fusion Proteins; D001617:beta-Glucosidase; D043364:Endo-1,4-beta Xylanases; C090001:XynB xylanase