title: Improving stability of nitrile hydratase by bridging the salt-bridges in specific thermal-sensitive regions.
abstract: The regions and types suitable mutations for bridging salt-bridges to intensify enzyme stability are identified in this study. Using nitrile hydratase (NHase) as the model enzyme, three deformation-prone thermal-sensitive regions (A1, A2 and A3 in β-subunit), identified by RMSF calculations of the thermophilic NHase 1V29 from Bacillus SC-105-1 and 1UGQ from Pseudonocardia thermophila JCM3095, were determined and the stabilized salt-bridge interactions were transferred into the corresponding region of industrialized mesophilic NHase-TH from Rhodococcus ruber TH. Three types of salt bridges-active-center-adjacent (in A1), internal neighboring-residue-bridged (in A2) and C-terminal-residue-bridged (A3)-were constructed in NHase-TH. The engineered NHase-TH-A1 showed reduced expression of β-subunit, reduced activity and irregular stability. NHase-TH-A2 exhibited a enhanced expression of β-subunit but complete loss of activity; while NHase-TH-A3 exhibited not only a slightly enhanced expression of β-subunit and enzyme activity, but also a 160% increase in thermal stability, a 7% enhanced product tolerance and a 75% enhanced resistance to cell-disruption by ultrasonication. The molecular dynamic (MD) simulation revealed that NHase-TH-A3, with a moderate RMSD value, generates 10 new salt bridges in both internal-subunit and interfacial-subunit, confirming that a C-terminal salt-bridge strategy is powerful for enzyme stability intensification through triggering global changes of the salt bridge networks.
authors: Department of Chemical Engineering, Tsinghua University, Beijing, China.
authors: Jie
authors: J
authors: Chen
authors: Huimin
authors: H
authors: Yu
authors: Changchun
authors: C
authors: Liu
authors: Jie
authors: J
authors: Liu
authors: Zhongyao
authors: Z
authors: Shen
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D004795:Enzyme Stability; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000201:enzymology; D006358:Hot Temperature; D006836:Hydro-Lyases / Q000737:chemistry* / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D008969:Molecular Sequence Data; D011487:Protein Conformation; D015202:Protein Engineering; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D006836:Hydro-Lyases; C048831:nitrile hydratase