An R-phycoerythrin stable in SDS solution at 37° C

Abstract

The spectral properties and the subunit components of an R-phycoerythrin that was stable at 37&deg;C in phosphate buffer (pH 7.0) with sodium dodecyl sulfate (SDS) were investigated. The R-phycoerythrin was obtained from the phycobilisome that was prepared from the marine red algae <i>Polysiphonia urceolata</i> by step-gradient sucrose centrifugation. By Sephadex G-150 column chromatography and polyacrylamide gel electrophoresis the R-phycoerythrin was prepared from the phycobilisome disassociatin that was incubated at 37¡C for 6 hr in 0.05M phosphate buffer (pH 7.0) containing 5% (w/v) SDS, 2% (w/v) mercaptoethanol and 10% (v/v) glycerol. The absorption spectrum of the R-phycoerythrin in 0.05M phosphate buffer (pH 7.0) showed that it has three absorption peaks at 498 nm, 537 nm and 566 nm, respectively; and therefore, it belongs to three-peak R-phycoerythrin. At room temperature, its fluorescence emission spectrum showed that the emission peak occurs at 578nm. The component analysis by SDS-polyacrylamide gel electrophoresis showed that the R-phycoerythrin is composed of 17.8 KD, 21 KD and 31KD of three colored polypeptides. Linker peptides existed in the R-phycoerythrin may account for its stability in SDS Solution at 37&deg;C. The stable feature, together with its high fluorescence emission efficiency, like most other phycobiliproteins, may let the obtained R-phycoerythrin be a promising agent of fluorescence label for diagnostic uses of various purposes.