title: A novel, intracellular antifreeze protein in an antarctic bacterium, Flavobacterium xanthum.
abstract: One strain of Antarctic bacteria, Flavobacterium xanthum IAM12026, has a highly active antifreeze protein (AFP) in the intracellular space. The cell-free extract from strain IAM12026 after culturing at 4 degree C for 7 days in TSB medium, had activity of 0.04 degree C at a concentration of 0.7 mg/ml. The ice crystals formed do not have distinct facets without typically rounded shape and the changes of their morphology during the course of the thermal hysteresis (TH) measurement. The ice crystal 'burst' occurring at the end-point of the TH is dendritic with hexagonal symmetry. Also, this activity was not affected by the treatment of dialysis and the addition of EDTA. Furthermore, this cell-free extract had high levels of ice recrystallization-inhibiting (RI) activity like those of Fish AFPs. The AFP (FlAFP) was homogeneity purified using chromatography. A relative molecular mass of approximately 59,000 was calculated from gel filtration and SDS-PAGE data. The thermal stability of FlAFP was below 50 degree C, and TH value was absent above 60 degree C. The TH value of FlAFP was activated at 5.2 degree C by the addition of 0.5 M malate. This activation was decreased with increasing protein concentration. To our knowledge this is the first report on the high level of TH and RI activities of bacterial intracellular AFP.
authors: Department of Biotechnology, Faculty of Engineering, Kansai University, Osaka, Japan. kawahara@ipcku.kansai-u.ac.jp
authors: Hidehisa
authors: H
authors: Kawahara
authors: Yoshiko
authors: Y
authors: Iwanaka
authors: Sakura
authors: S
authors: Higa
authors: Naomi
authors: N
authors: Muryoi
authors: Mika
authors: M
authors: Sato
authors: Michinori
authors: M
authors: Honda
authors: Hironori
authors: H
authors: Omura
authors: Hitoshi
authors: H
authors: Obata
mesh_terms: D000064:Acclimatization / Q000502:physiology; D000864:Antarctic Regions; D021301:Antifreeze Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D003080:Cold Temperature; D004591:Electrophoresis, Polyacrylamide Gel; D005417:Flavobacterium / Q000145:classification / Q000378:metabolism*; D008828:Microbiological Techniques; D008970:Molecular Weight
chemical_list: D021301:Antifreeze Proteins; D001426:Bacterial Proteins