A phycourobilin-containing phycoerythrin from the cyanobacterium Oscillatoria sp.

A filamentous cyanobacterium Oscillatoria sp. was isolated from a thermal spring of the Kamchatka peninsula. It contained a phycoerythrin unusual for cyanobacteria in that it had a phycourobilin prosthetic group. The absorption spectrum of the native purified phycoerythrin displayed maxima at 498 and 567 nm. The phycoerythrin comprised α- and β-subunits of molecular weights 18,700 and 19,800, respectively, in 1:1 stoichiometry. Polyacrylamide gel isoelectric focusing revealed one protein band at pI 4.6. The α- and β-subunits differed in their chromophore composition and content: α-subunit carried two phycoerythrobilins while the β-subunit had three phycoerythrobilins and one phycourobilin. The chromophore composition of all known phycoerythrins of cyanobacteria and red algae were compared, and on the basis of this comparative study designations C- to C-phycoerythrin were proposed for cyanobacterial red pigments. © 1985 Springer-Verlag.