title: The roles of surface loop insertions and disulfide bond in the stabilization of thermophilic WF146 protease.
abstract: Thermophilic WF146 protease possesses four surface loop insertions and a disulfide bond, resembling its psychrophilic (subtilisins S41 and S39) and mesophilic (subtilisins SSII and sphericase) homologs. Deletion of the insertion 3 (positions 193-197) or insertion 4 (positions 210-221) of WF146 protease resulted in a significant decrease of the enzyme stability. In addition, substitution of the residues Pro211 and Ala212 or residue Glu221 which localized in the vicinity of a Ca(2+) binding site of the enzyme by the corresponding residues in subtilisin S41 remarkably reduced the half-life of the enzyme at 70 degrees C, suggesting that the three residues contributed to the thermostability of the enzyme, probably by enhancing the affinity of enzyme to Ca(2+). In the presence of dithiothreitol, the WF146 protease suffered excessive autolysis, indicating that the Cys52-Cys65 disulfide bond played a critical role in stabilizing the WF146 protease against autolysis. The autolytic cleavage sites of the WF146 protease were identified to locate between residues Asn63-Gly64 and Cys65-Ala66 by N-terminal amino acid analysis of the autolytic product. It was noticed that the effect of the autolytic cleavage at Asn63-Gly64 could be compensated by the disulfide bond Cys52-Cys65 under non-reducing condition, and the disulfide bond cross-linked autolytic product remained active. The apparent stabilization effect of the disulfide bond Cys52-Cys65 in the WF146 protease might provide a rational basis for improving the stability of subtilase against autolysis by protein engineering.
authors.affiliation: College of Life Sciences, Wuhan University, Wuhan 430072, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Bian
authors.forename: Xiaoliang
authors.initials: X
authors.lastname: Liang
authors.forename: Nan
authors.initials: N
authors.lastname: Fang
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Tang
authors.forename: Bing
authors.initials: B
authors.lastname: Tang
authors.forename: Ping
authors.initials: P
authors.lastname: Shen
authors.forename: Zhenrong
authors.initials: Z
authors.lastname: Peng
mesh_terms: D000595:Amino Acid Sequence; D001407:Bacillus / Q000201:enzymology / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D003545:Cysteine / Q000737:chemistry; D004269:DNA, Bacterial / Q000235:genetics; D004795:Enzyme Stability; D006358:Hot Temperature; D007700:Kinetics; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D016297:Mutagenesis, Site-Directed; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013381:Subtilisins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011994:Recombinant Proteins; D010447:Peptide Hydrolases; D013381:Subtilisins; D003545:Cysteine