R-PHYCOERYTHRIN FROM THE RED ALGA GRACILARIA-LONGA

The red macroalga Gracilaria longa has been investigated for its phyco erythrin content. Absorption and emission spectra of this accessory pi gment, purified by gel filtration (A(565)/A(280)greater than or equal to 14.5), showed the typical spectroscopic behaviour of R-phycoerythri n, Absorption maxima were detected at 498, 538 and 565 nm, whereas the emission maximum was observed at 578 nm. The epsilon M (565 nm), calc ulated for the 'native' hexameric phycoerythrin (260000) was 1.03 x 10 (6) M(-1)cm(-1), each hexamer bearing 25 phycoerythrobilins and nine p hycourobilins. The circular dichroism spectrum showed three positive p eaks in the region from 495 to 570 nm and two negative bands at 210 an d 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) correspondin g to alpha, beta, gamma and gamma' chains. Isoelectric focusing resolv ed two pairs of major bands, at pI 4.30, 4.35 and pI 4.50, 4.55, and o ne pair of minor bands at pI 4.70, 4.75.