Poster Annual Conference of the Genetics Society of Australasia with the NZ Society for Biochemistry & Molecular Biology

Purification and chromophore composition of an unusual phycoerythrin from New Zealand red alga, Polysiphonia strictissima (771)

Pauline I Uyseco 1 , Malcolm T Rutledge 1 , Sigurd M Wilbanks 1
  1. University of Otago, North Dunedin, DUNEDIN, New Zealand

Phycoerythrin is a water soluble photosynthetic protein present in cryptomonads, cyanobacteria, and red algae. The relative amounts of its constituent chromophores, phycourobilin and phycoerythrobilin,  determines phycoerythrin's spectral properties and commercial value. Phycourobilin absorbs light at 495 nm, and phycoerythrobilin at 565 nm. With an absorption at 495 nm, and emission wavelength of 575 nm, phycoerythrin is a complementary dye to other dyes, such as fluorescein. With its absorption coefficient and great Stokes shift, phycourobilin-rich phycoerythrin offers enhanced sensitivity for biomedical assays. A phycourobilin-rich phycoerythrin was purified from the New Zealand red algae, Polysiphonia strictissima, obtained from the Otago Harbour, and characterised. Purification used differential ammonium sulfate precipitation and anion exchange chromatography. The subunits were then separated by reverse phase chromatography and the ratios of chromophores associated with each subunit were then determined by visual absorption spectroscopy. Peptides containing one chromophore will be generated and characterised by de novo sequencing using mass spectrometry to establish at which residue chromophores are covalently attached. P. strictissima harvested in the summer carries two phycoerythrobilin chromophores on its Ongoing analysis suggests that during autumn there is a rise in the phycourobilin content of phycoerythrin from P. strictissima. Complete analysis of the seasonal variation of this phycoerythrin will determine its potential commercial value, how the seasons affect this, and potentially determining the ideal time for harvest.