http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1518626
Chlorosomes are the main light harvesting complexes of green photosynthetic bacteria. Recently, a lamellar model was proposed for the arrangement of pigment aggregates in Chlorobium tepidum chlorosomes, which contain bacteriochlorophyll (BChl) c as the main pigment. Here we demonstrate that the lamellar organization is also found in chlorosomes from two brown-colored species (Chl. phaeovibrioides and Chl. phaeobacteroides) containing BChl e as the main pigment. This suggests that the lamellar model is universal among green sulfur bacteria. In contrast to green-colored Chl. tepidum, chlorosomes from the brown-colored species often contain domains of lamellar aggregates that may help them to survive in extremely low light conditions. We suggest that carotenoids are localized between the lamellar planes and drive lamellar assembly by augmenting hydrophobic interactions. A model for chlorosome assembly, which accounts for the role of carotenoids and secondary BChl homologs, is presented.
This study was supported by Academy of Finland grants (206926 and 211986 to R.T.; 208661 to S.B.) Czech Science Foundation and Czech Ministry of Education, Youth, and Sports (contracts 206/05/2739 and MSM0021620835 to J.P.), and the Spanish Ministry of Education and Science (No. BFU2004-04914-C02-02/BMC).
Peer reviewed