Isolation and characterization of macromolecular protein R-Phycoerythrin from Portieria hornemannii.

R-Phycoerythrin (R-PE) is one of the three phycobiliproteins which are extensively used as fluorescent probes, and it is prepared from red macro-algae. This macromolecular protein has gained importance in many biotechnological applications in food science, immunodiagnostic, therapy, cosmetics, protein and cell labeling, and analytical processes. In the present investigation, R-PE was isolated and purified from a red alga Portieria hornemannii. R-PE extracted and purified through ammonium sulfate precipitation (55%) followed by Q-Sepharose column chromatography had yielded a maximum purity of 5.2%. R-PE exhibited a typical "three-peak" with absorption maxima at 499, 545 and 565 nm. CD spectrum of R-PE yielded the following secondary structure data: alpha helix (14.30%), beta helix (28.10%), turn helix (19.20%) and random coil helix (38.40%). The molecular mass of R-PE was 240 kDa under Native-PAGE. Three different subunits such as α, β and γ of 16 kDa, 21 kDa and 39 kDa were segregated under SDS-PAGE. On two dimensional gel electrophoresis, one basic and four acidic subunits were detected. Five different tryptic peptides were assigned under MALDI-TOF. The sequences of N-terminus of R-PE of 10 different amino acids are Met Lys Gln Met Trp Asp Arg Met Val Val. The preparative procedures of the R-PE extraction and purification established based on the experiments exhibit advantages and can offer a reference for R-PE preparation from other marine red macro-alga P. hornemannii.