Chlorophyll-Protein Complexes of the Cyanophyte, Nostoc sp.

Abstract

Four chlorophyll-protein complexes were resolved from the cyanophyte, Nostoc sp., by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis at 4.degree. C. Complexes solubilized by SDS from Spinacia oleracea were run for comparison. As has been well documented, the P700-chlorophyll a-protein complex from the higher plant and blue-gree algal samples are similar, and the light-harvesting pigment protein complex is present only in the former. Most noteworthy are 2 closely migrating chlorophyll proteins in Nostoc sp. which have approximately the same mobility as a single chlorophyll-protein band resolvable from spinach. The absorption maximum of the complex from spinach is at 667 nm, and those of the 2 complexes from Nostoc sp. are at 667 and 669 nm; the fluorescence emission maximum at -196.degree. C is at 685 nm, and the 735 nm fluorescence peak, characteristic of the P700-chlorophyll a-protein complex, is absent. The apoproteins of these new complexes from Nostoc sp. and spinach are in the kilodalton range. At least one of these 2 chlorophyll-protein complexes from Nostoc sp. apparently compares with those recently described by others from higher plants and green algae as likely photosystem II complexes, perhaps containing P680, although no photochemical data are yet available.