15-Cis-carotenoids found in the reaction center of a green sulfur bacterium Chlorobium tepidum and in the Photosystem I reaction center of a cyanobacterium Synechococcus vulcanus

Carotenoids were extracted, at similar to 4 degrees C in complete darkness and under nitrogen atmosphere, from the reaction center (RC) of a green-sulfur bacterium and the Photosystem (PS) I RC of a cyanobacterium; each extract was subjected to high-performance liquid chromatography (HPLC) using an apparatus equipped with a two-dimensional diode-array detector in order to spectroscopically identify cis-trans carotenoids while performing HPLC analysis. In the extract from the RC of Chlorobium tepidum, 15-cis and all-trans-gamma-carotenes as well as 13-cis-, 15-cis- and all-trans-chlorobactenes (in the order of elution) were identified, whereas in the extract from the PS I RC of Synechococcus vulcanus, 15-cis-, all-trans- and 9-cis-beta-carotenes were found. Thus, the universal presence of 15-cis carotenoids in the 'iron sulfur-type' RCs has been shown in addition to the previous cases of the 'quinone-type' RCs.