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PLoS One. 2014 Jul 03;9(7):e101724. doi: 10.1371/journal.pone.0101724. eCollection 2014.

Isolation, purification and properties of an R-phycocyanin from the phycobilisomes of a marine red macroalga Polysiphonia urceolata.

PloS one

Lu Wang, Yanyan Qu, Xuejun Fu, Mingri Zhao, Shumei Wang, Li Sun

PMID: 24992364 PMCID: PMC4081778 DOI: 10.1371/journal.pone.0101724


Phycobilisomes were prepared from a marine red macroalga Polysiphonia urceolata (P. urceolata) by sucrose step-gradient ultracentrifugation. From the prepared phycobilisomes, an R-phycocyanin was isolated by gel filtration on Sephadex G-150 and then purified by ion exchange chromatography on DEAE-Sepharose Fast Flow and native polyacrylamide gel electrophoresis (PAGE) performed in neutral buffer systems. The purified R-phycocyanins showed not only a homogeneous trimer of 136 kDa in gel filtration and a single band in native PAGE, but also exhibited one band at about pH 5.7 in native isoelectric focusing (IEF). By a gradient SDS-PAGE the purified R-phycocyanin was determined to contain one a subunit of 17.5 kDa (α17.5) and two b subunits of 21.3 kDa and 22.6 kDa (β21.3 and β22.6). The analysis from denaturing isoelectric focusing and two-dimension PAGE demonstrated that α17.5, β21.3 and β22.6 had their pIs of 6.4, 5.3 and 5.4, respectively. Furthermore, mass spectroscopy analysis of β21.3 and β22.6 by MALDI-TOF mass spectrometry demonstrated the two b subunits had differences in peptide mass fingerprinting. These results revealed that the prepared R-phycocyanins were composed of one a and two b subunits. (α17:53 β21:32 β22:61) and (α17:53 β21:31 β22:62), which have a structural foundation to show their pIs too close for them to be definitely resolved by native IEF, are postulated to be the most possible trimeric forms of the R-phycocyanins prepared from the phycobilisomes of P. urceolata.


  1. PLoS One. 2014 Feb 04;9(2):e87833 - PubMed

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