期刊
MARINE BIOTECHNOLOGY
卷 16, 期 5, 页码 502-512出版社
SPRINGER
DOI: 10.1007/s10126-014-9567-y
关键词
Antifreeze proteins; Antarctic marine prasinophyte; Ice binding; Thermal hysteresis; In silico protein modeling
资金
- Korea Research Council of Fundamental Science and Technology (KRCF)
- Korea Polar Research Institute (KOPRI) [PG12010]
- Korea CCS R&D Center (KCRC) - Korean government (Ministry of Science, ICT and Future Planning)
- Canadian Institutes for Health Research
- National Research Council of Science & Technology (NST), Republic of Korea [pg12010] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
Antifreeze proteins (AFPs) play an important role in the psychrophilic adaptation of polar organisms. AFPs encoded by an Antarctic chlorophyte, identified as Pyramimonas gelidicola, were isolated and characterized. Two AFP isoforms were found from cDNAs and their deduced molecular weights were estimated to be 26.4 kDa (Pg-1-AFP) and 27.1 kDa (Pg-2-AFP). Both AFP cDNAs were cloned and expressed in Escherichia coli. The purified recombinant Pg-1-rAFP and Pg-2-rAFP both showed antifreeze activity based on the measurement of thermal hysteresis (TH) and morphological changes to single ice crystals. Pg-1-rAFP shaped ice crystals into a snowflake pattern with a TH value of 0.6 +/- 0.02 A degrees C at similar to 15 mg/ml. Single ice crystals in Pg-2-rAFP showed a dendritic morphology with a TH value of 0.25 A +/- 0.02 A degrees C at the same protein concentration. Based on in silico protein structure predictions, the three-dimensional structures of P. gelidicola AFPs match those of their homologs found in fungi and bacteria. They fold as a right-handed beta-helix flanked by an alpha-helix. Unlike the hyperactive insect AFPs, the proposed ice-binding site on one of the flat beta-helical surfaces is neither regular nor well-conserved. This might be a characteristic of AFPs used for freeze tolerance as opposed to freeze avoidance. A role for P. gelidicola AFPs in freeze tolerance is also consistent with their relatively low TH values.
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