Internal structure of chlorosomes from brown-colored chlorobium species and the role of carotenoids in their assembly.
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.
Psencík
Jakub
J
Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic.
Arellano
Juan B
JB
Ikonen
Teemu P
TP
Borrego
Carles M
CM
Laurinmäki
Pasi A
PA
Butcher
Sarah J
SJ
Serimaa
Ritva E
RE
Tuma
Roman
R
D001429:Bacteriochlorophylls / Q000737:chemistry* / Q000378:metabolism; D002338:Carotenoids / Q000737:chemistry* / Q000378:metabolism; D041883:Chlorobium / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D003198:Computer Simulation; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure*; D008954:Models, Biological; D008956:Models, Chemical; D015388:Organelles / Q000737:chemistry / Q000648:ultrastructure
D001429:Bacteriochlorophylls; D045342:Light-Harvesting Protein Complexes; D002338:Carotenoids