title: Expression, purification, and antifreeze activity of carrot antifreeze protein and its mutants.
abstract: Antifreeze proteins (AFPs) enable organisms to survive under freezing or sub-freezing conditions. AFPs have a great potential in the low temperature storage of cells, tissues, organs, and foods. This process will require a large number of recombinant AFPs. In the present study, the recombinant carrot AFP was highly expressed in Escherichia coli strain BL21 (DE3). The activity of the purified and refolded recombinant proteins was analyzed by measurement of thermal hysteresis (TH) activity and detection of in vitro antifreeze activity by measuring enhanced cold resistance of bacteria. Two carrot AFP mutants generated by site-directed mutagenesis were also expressed and purified under these conditions for use in parallel experiments. Recombinant DcAFP displayed a TH activity equivalent to that of native DcAFP, while mutants DcAFP-N130Q and rDcAFP-N130V showed 32 and 43% decreases in TH activity, respectively. Both the recombinant DcAFP and its mutants were able to enhance the cold resistance of bacteria, to degrees consistent with their respective TH activities.
authors.affiliation: The Key Laboratory of Gene Engineering of Ministry of Education, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China.
authors.forename: Dang-Quan
authors.initials: DQ
authors.lastname: Zhang
authors.forename: Bing
authors.initials: B
authors.lastname: Liu
authors.forename: Dong-Ru
authors.initials: DR
authors.lastname: Feng
authors.forename: Yan-Ming
authors.initials: YM
authors.lastname: He
authors.forename: Jin-Fa
authors.initials: JF
authors.lastname: Wang
mesh_terms: D021301:Antifreeze Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001483:Base Sequence; D017931:DNA Primers; D018552:Daucus carota / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D010957:Plasmids; D011994:Recombinant Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D021301:Antifreeze Proteins; D017931:DNA Primers; D011994:Recombinant Proteins