title: Biosynthetic production of type II fish antifreeze protein: fermentation by Pichia pastoris.
abstract: Sea raven type II antifreeze protein (SRAFP) is one of three different fish antifreeze proteins isolated to date. These proteins are known to bind to the surface of ice and inhibit its growth. To solve the three-dimensional structure of SRAFP, study its ice-binding mechanism, and as a basis for engineering these molecules, an efficient system for its biosynthetic production was developed. Several different expression systems have been tested including baculovirus, Escherichia coli and yeast. The latter, using the methylotrophic organism Pichia pastoris as the host, was the most productive. In shake-flask cultures the levels of SRAFP secreted from Pichia were up to 5 mg/l. The recombinant protein has an identical activity to SRAFP from sea raven serum. In order to increase yields further, four different strategies were tested in 10-l fermentation vessels, including: (1) optimization of pH and dissolved oxygen, (2) mixed feeding of methanol and glycerol with Mut(s) clones, (3) supplementation of amino acid building blocks, and (4) methanol feeding with Mut+ clones. The mixed-feeding/Mut(s) strategy proved to be the most efficient with SRAFP yields reaching 30 mg/l.
authors.affiliation: Department of Biochemistry, Queen's University, Kingston, Ontario, Canada.
authors.forename: M C
authors.initials: MC
authors.lastname: Loewen
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.forename: P L
authors.initials: PL
authors.lastname: Davies
authors.forename: A J
authors.initials: AJ
authors.lastname: Daugulis
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D021341:Antifreeze Proteins, Type II; D002352:Carrier Proteins / Q000096:biosynthesis*; D003470:Culture Media; D005285:Fermentation; D005399:Fishes / Q000235:genetics; D005990:Glycerol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D000432:Methanol / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010843:Pichia / Q000378:metabolism*; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis*
chemical_list: D000596:Amino Acids; D021341:Antifreeze Proteins, Type II; D002352:Carrier Proteins; D003470:Culture Media; D011993:Recombinant Fusion Proteins; C089666:antifreeze protein, sea raven; D005990:Glycerol; D010100:Oxygen; D000432:Methanol