Light- and MgCl2-dependent characteristics of four chlorophyll-protein complexes isolated from the marine dinoflagellate,Glenodinium sp.

Chlorophyll-protein complexes previously isolated from low-light (80 μE·m⁻²·s⁻¹) log cultures of the marine dinoflagellate, Glenodinium sp., were further characterized. SDS solubilization in combination with polyacrylamide gel electrophoresis in the presence of Deriphat 160-C resolved four discrete chlorophyll-protein bands. In order to elucidate the functional role of Glenodinium sp., room-temperature absorption and fluorescence spectra, protein composition, and pigment molar ratios were obtained for each complex. Results indicated that complex I was analogous to the green plant Photosystem I complex and was also associated with light-harvesting chlorophyll c₂. Complex II was highly enriched in chlorophyll c₂, devoid of peridinin, and demonstrated energy transfer from chlorophyll c to chlorophyll a within the complex, indicating the presence of a light-harvesting component. Based on peridinin: chlorophyll a ratios and fluorescence excitation spectra analyses for complexes III and IV, it was concluded that these complexes contained functional peridinin-chlorophyll a-protein complexes. Changing the ionic environment during isolation of the complexes, or altering the growth irradiance of Glenodinium sp. cultures, resulted in a significant alteration of distribution of chlorophyll a among the chlorophyll-protein complexes.