earticle

영어

In the diatom Cylindrotheca fusiformis, modified peptides called silaffin polypeptides are responsible for silica deposition in vivo at ambient conditions. Recently, it is discovered that the synthetic R5 peptide, the repeat unit of silaffin polypeptide without post-translational modification, was capable of precipitating silica in vitro as well at ambient conditions. Herein, green fluorescent protein (GFP) chimeric proteins were generated by incorporating synthetic silaffin R5 peptides and related unmodified silaffin domains (R1-R7) from Cylindrotheca fusiformis onto GFP by recombinant DNA technology and their ability to cause silicification examined. GFP chimeric proteins showed silicification at very low concentrations (600-700 μg/ml), compared to adding excess amounts of R5 peptides (10 mg/ml) as previously reported. Sensitive to pH conditions, only the GFP-R1 chimera showed silicification activity at pH 8.0. The protein immobilization efficiencies of these chimeras were unexpectedly high ranging from 75 to 85%, with the R1 silaffin-protein construct showing excellent immobilization efficiency and a constant molar ratio of silica to protein ranging from 250-350 over a wide pH range. The average silica particle sizes had a tendency to decrease as pH increased to basic conditions. This study demonstrated the production of nanoscale immobilized protein, fabricated via silaffin-fused proteins.