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A new phycocyanin(PC) fluorescent subunit namedβ_2(18kDa) was isolated and characterized by both SDS-PAGE and isoelectric focusing(IEF) from a species of cryptophytic alga Chroomonas placoidea.PC was separated and purified by ammonium sulfate sedimentation followed by two steps of Sephadex G-100 chromatography.After denatured in 4 mol/L urea for 48 h,PC was divided into two fractions by passing through a Sephacryl S-100 chromatography column twice.The blue fraction(S-1) containedβsubunits with a maximal absorbance at 595 nm in visible light region.While the green fraction(S-2) enriched inαsubunits showed a characteristic long wavelength absorbance at 680-700 nm region and exhibited a relatively low molecular weight of 9.4(α_1) and 8.5 kDa(α_2).Fraction S-1 also consisted of two different fluorescent subunits with molecular weight of 20.1 kDa(β_1) and 18 kDa (β_2) and differed from each other on isoelectric points of pH 5.7(ft) and 6.0(ft),respectively.Further investigation of peptide sequence will help a lot in elucidating the new subunit ft that was smaller in size and more neutral than the known ft subunit,and may provide an alternative explanation in structure of cryptophytic phycobiliproteins.
A new phycocyanin (PC) fluorescent subunit named β_2 (18kDa) was isolated and characterized by both SDS-PAGE and isoelectric focusing (IEF) from a species of cryptophytic alga Chroomonas placoidea. PC was separated and purified by ammonium sulfate sedimentation followed by two steps of Sephadex G-100 chromatography. After denatured in 4 mol / L urea for 48 h, PC was divided into two fractions by passing through a Sephacryl S-100 chromatography column twice. Blue fraction (S-1) contained βsubunits with a maximal absorbance at 595 nm in visible light region. Wide fraction (S-2) enriched in αsubunits showed a characteristic long wavelength absorbance at 680-700 nm region and exhibited a relatively low molecular weight of 9.4 (α_1) and 8.5 kDa (α_2). Fraction S-1 also consisted of two different fluorescent subunits with molecular weight of 20.1 kDa (β_1) and 18 kDa (β_2) and differed from each other on isoelectric points of 5.7 (ft) and 6.0 (ft), respectively. pe ptide sequence will help a lot in elucidating the new subunit ft that was smaller in size and more neutral than the known ft subunit, and may provide an alternative explanation in structure of cryptophytic phycobiliproteins.