The major light-harvesting protein complex in Acaryochloris marina

Abstract

The major light-harvesting protein complex with chlorophyll d has been isolated from Acaryochloris marina. The separation was achieved by solubilising the thylakoid membranes with a mixture of detergents: dodecyl maltoside, octyl glucoside and zwittergent 3-14; the best solubilisation rate was ca.70% with the detergent:chlorophyll ratio of 10:1. Once solubilised, the chlorophyll-binding complexes were separated using linear sucrose density gradients (6-40%) and ultracentrifuged at 150 000 x g for 16 h. The major light-harvesting complexes from the gradients were then characterised using non-denaturing and SDS-PAGE electrophoresis; the pigment content was estimated by HPLC and spectral analysis used both absorbance and fluorescence spectroscopy. The data indicate that the main polypeptide of the light-harvesting complex is ca. 35kDa, and the main pigment is chlorophyll d; however, carotenoids and a small amount of chlorophyll a are present. The level of chlorophyll a appears to be variable depending on the culture conditions.