R-PHYCOERYTHRIN FROM THE RED ALGA GRACILARIA-LONGA

The red macroalga Gracilaria longa has been investigated for its phycoerythrin content. Absorption and emission spectra of this accessory pigment, purified by gel filtration (A(565)/A(280)greater than or equal to 14.5), showed the typical spectroscopic behaviour of R-phycoerythrin, Absorption maxima were detected at 498, 538 and 565 nm, whereas the emission maximum was observed at 578 nm. The epsilon M (565 nm), calculated for the 'native' hexameric phycoerythrin (260000) was 1.03 x 10(6) M(-1)cm(-1), each hexamer bearing 25 phycoerythrobilins and nine phycourobilins. The circular dichroism spectrum showed three positive peaks in the region from 495 to 570 nm and two negative bands at 210 and 222 rim. The alpha-helix content, calculated from CD data, was 65%. On SDS-polyacrylamide electrophoresis, the R-phycoerythrin dissociated into four coloured bands (19000, 21500, 30000 and 33000) corresponding to alpha, beta, gamma and gamma' chains. Isoelectric focusing resolved two pairs of major bands, at pI 4.30, 4.35 and pI 4.50, 4.55, and one pair of minor bands at pI 4.70, 4.75.