The Study For R-Phycoerythrins Of The Phycobilisome Rod Subdomain From Polysiphoia Urceolata Grev

The marine red macroalga of Polysiphoia urceolata Grev,which is rich and easily collected inthe Yantai shore area of the Huanghai,was used to extract R-phycoerythrin?R-PE?in lower salt solution and phycobilisomes?PBSs?in higher salt solution.According to the pricinple of multi-dementional chromatography,the two R-PE proteins different in the structural properties of net electronic charge and hydrophobicity were isolated and purified by combining the gel fitration on Sephacry S-300 column?S-300?with the ion exchange chromatography of DEAE Sepharose Fast Flow and the hydrophobic interaction chromatography on Butyl Sepharose 4 Fast Flow column.The two R-PEs showed a single band in Native-PAGE and Native-IEF,and had the different pIs of R-PEI 4.7 and R-PEII 4.6,respectively.The SDS-PAGE analysis demonstrated that R-PEI and R-PEII had the same subunits of?,?,?₁,?₂,????and???₁?and the colorless linker polypeptide.Except that R-PEI showed the light absorption in 250 nm to 400 nm a slight higher than R-PEII,the both of them had the same spectra of flouroscence and the absorption from 400 nm to 750 nm.These results demonstrated that R-PEI and R-PEII were the two R-PEs of Polysiphoia urceolata which had very similar spectral properties and showed minor different structural characteristics.The hexamer R-PEs and the R-PE complexes larger than hexamer R-PE were isolated from the partial disassociated intact phycobilisomes in 200 mmol/L phosphrate buffer by the density gradient ultracentrifugation.Although both of them showed a single band in Native-PAGE,but the R-PE complexes larger than hexamer R-PE exhibited two bands with different pIs,indicating that the R-PE complexes should be the complexes made up of R-PEI and R-PEII.The results from SDS-PAGE analysis demonstrated that the hexamer R-PE and R-PE complex both contained the subunits of?,?and?₁ and no colorless polypeptide,but the?₂ subunint only existed in the R-PE complex.Obviously,on the one hand the?₂ subunint takes part in the formation of the stable R-PE complexs which are larger than hexamer R-PEs;the?₂ subunint as linker polypeptide linked two trimer R-PE on the other hand.This relatively stable R-PE complex connects with the core subdomain of phycobilisomes via the R-phycocyanin.The hexamer R-PE disassociated easily from the intact phycobilisomes should exist in the R-PE complexes with relatively less stability.The assemply of the two types of the R-PE complexes in the rod subdomain needs to be determined by further investigations.