title: A hyperactive, Ca2+-dependent antifreeze protein in an Antarctic bacterium.
abstract: In cold climates, some plants and bacteria that cannot avoid freezing use antifreeze proteins (AFPs) to lessen the destructive effects of ice recrystallization. These AFPs have weak freezing point depression activity, perhaps to avoid sudden, uncontrolled growth of ice. Here, we report on an uncharacteristically powerful bacterial AFP found in an Antarctic strain of the bacterium, Marinomonas primoryensis. It is Ca(2+)-dependent, shows evidence of cooperativity, and can produce over 2 degrees C of freezing point depression. Unlike most AFPs, it does not produce obvious crystal faceting during thermal hysteresis. This AFP might be capable of imparting freezing avoidance to M. primoryensis in ice-covered Antarctic lakes. A hyperactive bacterial AFP has not previously been reported.
authors.affiliation: Department of Biochemistry and the Protein Engineering Network of Centres of Excellence, Queen's University, Kingston, Ont., Canada K7L 3N6.
authors.forename: Jack A
authors.initials: JA
authors.lastname: Gilbert
authors.forename: Peter L
authors.initials: PL
authors.lastname: Davies
authors.forename: Johanna
authors.initials: J
authors.lastname: Laybourn-Parry
mesh_terms: D000864:Antarctic Regions; D021301:Antifreeze Proteins / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D003081:Cold Climate; D003460:Crystallization; D005618:Fresh Water / Q000382:microbiology*; D020563:Gammaproteobacteria / Q000254:growth & development / Q000378:metabolism*; D007053:Ice
chemical_list: D021301:Antifreeze Proteins; D001426:Bacterial Proteins; D007053:Ice; D002118:Calcium