title: High-level expression, secretion, and purification of the thermostable aqualysin I from Thermus aquaticus YT-1 in Pichia pastoris.
abstract: Aqualysin I is a heat-stable subtilisin-type serine protease which is secreted into the culture medium by Thermus aquaticus YT-1, an extreme thermophile. We report the high-level expression of an aqualysin I protein using its native signal sequence for secretion in the methylotrophic yeast, Pichia pastoris. The expression of aqualysin I in P. pastoris was carried out using the glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter. Pro-aqualysin I (38kDa) as inactive protein was secreted into the medium of shake-flask cultures at a concentration of 1g/L. It was isolated from the culture supernatant by an ammonium sulfate precipitation and one-step anion exchange chromatography in a nearly pure form and was autoproteolytically activiated by heat treatment. A proteolytic activity test indicated that the purified recombinant aqualysin I was properly folded with a specific activity similar to that of the native enzyme. We also explored the possibility of secreting the GAP expressed aqualysin I in P. pastoris by in-frame fusion of the Saccharomyces cerevisiae alpha-factor secretion signal. However, the levels of secreted pro-aqualysin I particles were approximately 10 times lower, possibly as a consequence of membrane association or to the influence of the alpha-factor secretion signal sequences on the transcription or secretion of aqualysin I. When considering further optimization of the downstream process and culture conditions for high-level production of recombinant aqualysin I by P. pastoris, this expression system is promising for development as an industrial process.
authors.affiliation: Department of Microbiology, Technical University of Gdańsk, ul. Narutowicza 11/12, 80-952 Gdańsk, Poland.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Oledzka
authors.forename: Sławomir
authors.initials: S
authors.lastname: Dabrowski
authors.forename: Józef
authors.initials: J
authors.lastname: Kur
mesh_terms: D000595:Amino Acid Sequence; D017931:DNA Primers / Q000235:genetics; D004795:Enzyme Stability; D006358:Hot Temperature; D008969:Molecular Sequence Data; D010843:Pichia / Q000201:enzymology* / Q000235:genetics; D010957:Plasmids / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D012697:Serine Endopeptidases / Q000096:biosynthesis* / Q000302:isolation & purification / Q000378:metabolism*; D013824:Thermus / Q000201:enzymology* / Q000235:genetics
chemical_list: D017931:DNA Primers; D011994:Recombinant Proteins; D012697:Serine Endopeptidases; C055102:aqualysin I