title: An extracellular halophilic protease SptA from a halophilic archaeon Natrinema sp. J7: gene cloning, expression and characterization.
abstract: A gene encoding an extracellular protease, sptA, was cloned from the halophilic archaeon Natrinema sp. J7. It encoded a polypeptide of 565 amino acids containing a putative 49-amino acid signal peptide, a 103-amino acid propeptide, as well as a mature region and C-terminal extension, with a high proportion of acidic amino acid residues. The sptA gene was expressed in Haloferax volcanii WFD11, and the recombinant enzyme could be secreted into the medium as an active mature form. The N-terminal amino acid sequencing and MALDI-TOF mass spectrometry analysis of the purified SptA protease indicated that the 152-amino acid prepropeptide was cleaved and the C-terminal extension was not processed after secretion. The SptA protease was optimally active at 50 degrees C in 2.5 M NaCl at pH 8.0. The NaCl removed enzyme retained 20% of its activity, and 60% of the activity could be restored by reintroducing 2.5 M NaCl into the NaCl removed enzyme. When the twin-arginine motif in the signal peptide of SptA protease was replaced with a twin-lysine motif, the enzyme was not exported from Hfx. volcanii WFD11, suggesting that the SptA protease was a Tat-dependent substrate.
authors.affiliation: College of Life Sciences, Wuhan University, Wuhan 430072, People's Republic of China.
authors.forename: Wanliang
authors.initials: W
authors.lastname: Shi
authors.forename: Xiao-Feng
authors.initials: XF
authors.lastname: Tang
authors.forename: Yuping
authors.initials: Y
authors.lastname: Huang
authors.forename: Fei
authors.initials: F
authors.lastname: Gan
authors.forename: Bing
authors.initials: B
authors.lastname: Tang
authors.forename: Ping
authors.initials: P
authors.lastname: Shen
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002364:Caseins / Q000378:metabolism; D003001:Cloning, Molecular; D004795:Enzyme Stability; D019617:Halobacterium salinarum / Q000201:enzymology* / Q000235:genetics; D019622:Haloferax volcanii / Q000235:genetics / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals; D011994:Recombinant Proteins / Q000737:chemistry; D020539:Sequence Analysis, Protein; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013696:Temperature
chemical_list: D019843:Archaeal Proteins; D002364:Caseins; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; C026018:azocasein; D012965:Sodium Chloride; D010447:Peptide Hydrolases