title: Comparison of functional properties of two fungal antifreeze proteins from Antarctomyces psychrotrophicus and Typhula ishikariensis.
abstract: Antifreeze proteins are structurally diverse polypeptides that have thermal hysteresis activity and have been discovered in many cold-adapted organisms. Of these, fungal antifreeze protein has been purified and partially characterized only in a species of psychrophilic basidiomycete, Typhula ishikariensis. Here we report a new fungal antifreeze protein from another psychrophile, Antarctomyces psychrotrophicus. We examined its biochemical properties and thermal hysteresis activity, and compared them with those of the T. ishikariensis antifreeze protein. The antifreeze protein from A. psychrotrophicus was purified and identified as an extracellular protein of approximately 28 kDa, which halved in size following digestion with glycosidase. The A. psychrotrophicus antifreeze protein generated bipyramidal ice crystals and exhibited thermal hysteresis activity (for example thermal hysteresis = 0.42 degrees C for a 0.48 mM solution) similar to that of fish antifreeze proteins, while a unique rugged pattern was created on the facets of the ice bipyramid. The thermal hysteresis activity of the A. psychrotrophicus antifreeze protein was maximized under alkaline conditions, while that of the T. ishikariensis antifreeze protein was greatest under acidic conditions. The T. ishikariensis antifreeze protein exhibited a bursting ice growth normal to the c-axis of the ice crystal and high thermal hysteresis activity (approximately 2 degrees C), as in the case of insect hyperactive antifreeze proteins. From these results, we speculate that the A. psychrotrophicus antifreeze protein is very different from the T. ishikariensis antifreeze protein, and that these two psychrophiles have evolved from different genes.
authors.affiliation: Research Institute of Genome-based Biofactory, National Institute of Advanced Industrial Science and Technology, Toyohira-ku, Sapporo, Japan.
authors.forename: Nan
authors.initials: N
authors.lastname: Xiao
authors.forename: Keita
authors.initials: K
authors.lastname: Suzuki
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Nishimiya
authors.forename: Hidemasa
authors.initials: H
authors.lastname: Kondo
authors.forename: Ai
authors.initials: A
authors.lastname: Miura
authors.forename: Sakae
authors.initials: S
authors.lastname: Tsuda
authors.forename: Tamotsu
authors.initials: T
authors.lastname: Hoshino
mesh_terms: D000595:Amino Acid Sequence; D000864:Antarctic Regions; D021301:Antifreeze Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001203:Ascomycota / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D001487:Basidiomycota / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003081:Cold Climate; D003460:Crystallization; D017931:DNA Primers / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D007053:Ice; D046448:Ice Cover / Q000382:microbiology; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: D021301:Antifreeze Proteins; D017931:DNA Primers; D004271:DNA, Fungal; D005656:Fungal Proteins; D007053:Ice