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Improving thermostability of ( R )‐selective amine transaminase from Aspergillus terreus through introduction of disulfide bonds
Author(s) -
Xie DongFang,
Fang Hui,
Mei JiaQi,
Gong JinYan,
Wang HongPeng,
Shen XiuYing,
Huang Jun,
Mei LeHe
Publication year - 2017
Publication title -
biotechnology and applied biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.468
H-Index - 70
eISSN - 1470-8744
pISSN - 0885-4513
DOI - 10.1002/bab.1572
Subject(s) - thermostability , aspergillus terreus , mutant , amine gas treating , stereochemistry , chemistry , transaminase , disulfide bond , mutagenesis , protein engineering , biochemistry , enzyme , organic chemistry , gene
To improve the thermostability of ( R )‐selective amine transaminase from Aspergillus terreus (AT‐ATA), we used computer software Disulfide by Design and Modelling of Disulfide Bonds in Proteins to identify mutation sites where the disulfide bonds were most likely to form. We obtained three stabilized mutants (N25C‐A28C, R131C‐D134C, M150C‐M280C) from seven candidates by site‐directed mutagenesis. Compared to the wild type, the best two mutants N25C‐A28C and M150C‐M280C showed improved thermal stability with a 3.1‐ and 3.6‐fold increase in half‐life ( t 1/2 ) at 40 °C and a 4.6 and 5.1 °C increase in T 50 10 . In addition, the combination of mutant R131C‐D134C and M150C‐M280C displayed the largest shift in thermostability with a 4.6‐fold increase in t 1/2 at 40 °C and a 5.5 °C increase in T 50 10 . Molecular dynamics simulation indicated that mutations of N25C‐A28C and M150C‐M280C lowered the overall root mean square deviation for the overall residues at elevated temperature and consequently increased the protein rigidity. The stabilized mutation of R131C‐D134C was in the region of high mobility and on the protein surface, and the disulfide bond constraints the flexibility of loop 121–136.