Abstract: Protein plastocyanin from a green alga, Ulva pertusa, has been purified. Samples were homogenized in 0.02 mol/L phosphate buffer (pH 7.2) and then centrifuged to remove debris and subjected to ammonium sulfate fractionation (40%-80% saturation). Ion exchange column chromatography with DEAE-Sepharose Fast Flow and gel filtration column chromatography with Sephadex G-75 were then employed for further purification of plastocyanin. Three peaks, A, B and C, were eluted with 0.01 mol/L phosphate buffer, containing a NaCl linear gradient from 0 to 1.0 mol/L at the flow rate of 32 mL/h through DEAE-Sepharose chromatography. The protein fractions containing the plastocyanin were then purified further with Sephardex G-75 column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophores (SDS-PAGE) is analysis indicates that the protein was purified to homogeneity and its relative molecular mass is 10000. N-terminal amino acid sequence was used to identify the protein. The protein was transblotted to PVDF membrane and N-terminal amino acid sequence was performed via Edman degradation with an automated amino acid sequencer. The 20 N-terminal amino acid residues are AAIVKLGPDDGSLAFVPSKI, which share 85% homology with the 20 N-terminal amino acid sequence of U. prolifera and U. arasakii, and share 90% homology with the ones of U. pertusa formerly reported.

Key words: N-terminal amino acid sequence , plastocynin, purification, Ulva pertusa, column chromatography