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Antifreeze proteins (AFPs) are produced by many species of teleost fish that inhabit potentially lethal ice-laden seawater and afford them protec-tion from freezing. To date type I AFPs have been fully characterized in two teleost orders: Pleuronectiformes and Scorpaeniformes. | IFEBS Journal Isolation and characterization of type I antifreeze proteins from cunner Tautogolabrus adspersus order Perciformes Rod S. Hobbs1 Margaret A. Shears1 Laurie A. Graham2 Peter L. Davies2 and Garth. L. Fletcher1 1 Ocean Sciences Centre Memorial university of Newfoundland Canada 2 Department of Biochemistry Queen s University Kingston Canada Keywords amino acid sequence cDNA sequence convergent evolution seasonalcycle thermalhysteresis Correspondence G. L. Fletcher Ocean Sciences Centre MemorialUniversity of Newfoundland St John s NLA1C 5S7 Canada Fax 1 709 864 3220 Tel 1 709 864 3276 E-mail fletcher@mun.ca or garthfletcher@nl.rogers.com Website http www.mun.ca osc Home Received 17 May 2011 revised 15 July 2011 accepted 29 July 2011 doi 10.1111 j.1742-4658.2011.08288.x Antifreeze proteins AFPs are produced by many species of teleost fish that inhabit potentially lethal ice-laden seawater and afford them protection from freezing. To date type I AFPs have been fully characterized in two teleost orders Pleuronectiformes and Scorpaeniformes. In this study we report the isolation and complete characterization of a type I AFP present in fish from a third order cunner Tautogolabrus adspersus order Perciformes family Labridae . This protein was purified from blood plasma and found to belong to what is now known as classical type I AFP with their small size mass 4095.16 Da alanine richness 57 mol high a-helicity 99 with the ability to undergo reversible thermal denaturation 11 amino acid ThrX10 repeat regions within the primary structure the capacity to impart a hexagonal bipyramidal shaping to ice crystals and the conservation of an ice-binding site found in many of the other type I AFPs. Partial de novo sequencing of the plasma AFP accounted for approximately half of the peptide mass. Sequencing of a combined liver and skin cDNA library indicated that the protein is produced without a signal sequence. In addition the translated product of the AFP cDNA suggests .