CsmA Protein is Associated with BChl a in the Baseplate Subantenna of Chlorosomes of the Photosynthetic Green Filamentous Bacterium Oscillochloris trichoides belonging to the Family Oscillochloridaceae

Abstract

The baseplate subantenna in chlorosomes of green anoxygenic photosynthetic bacteria, belonging to the families Chloroflexaceae and Chlorobiaceae, is known to represent a complex of bacteriochlorophyll (BChl) a with the ~6 kDa CsmA proteins. Earlier, we showed the existence of a similar BChl a subantenna in chlorosomes of the photosynthetic green bacterium Oscillochloris trichoides, member of Oscillochloridaceae, the third family of green photosynthetic bacteria. However, this BChl a subantenna was not visually identified in absorption spectra of isolated Osc. trichoides chlorosomes in contrast to those of Chloroflexaceae and Chlorobiaceae. In this work, using room and low-temperature absorbance and fluorescence spectroscopy and sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis of alkaline-treated and untreated chlorosomes of Osc. trichoides, we showed that the baseplate BChl a subantenna does exist in Oscillochloridaceae chlorosomes as a complex of BChl a with the 5.7 kDa CsmA protein. The present results support the idea that the baseplate subantenna, representing a complex of BChl a with a ~6 kDa CsmA protein, is a universal interface between the BChl c subantenna of chlorosomes and the nearest light-harvesting BChl a subantenna in all three known families of green anoxygenic photosynthetic bacteria.

Reconstruction of bacteriochlorophyll biosynthesis pathways in the filamentous anoxygenic phototrophic bacterium Oscillochloris trichoides DG-6 and evolution of anoxygenic phototrophs of the order Chloroflexales

“…The molecular masses of CsmA of Chlorobium tepidum, Cfl. aurantiacus and O. trichoides are 6.2, 5.7 and 6.0 kDa, respectively (Bryant et al, 2002Frigaard et al, 2003;Frigaard & Bryant, 2004;Montaño et al, 2003;Zobova et al, 2011). The CsmA polypeptide is typically the most abundant chlorosome protein in Cfl.…”

Orientation of B798 BChl a Q y transition dipoles in Chloroflexus aurantiacus chlorosomes: polarized transient absorption spectroscopy studies

“…aurantiacus chlorosomes (Pšenčik et al 2009). The chlorosome envelopes of chlorosomes from all species of green photosynthetic bacteria contain several polypeptides (Niedermeier et al 1994;Sakuragi et al 1999;Frigaard and Bryant 2006;Zobova et al 2011;Taisova et al 2012). CsmA is the smallest (*6 kDa) and most abundant of these proteins (Frigaard and Bryant 2006).…”

“…aurantiacus (Montano et al 2003;Sakuragi et al 1999), Osc. trichoides (Zobova et al 2011;Taisova et al 2012) and Chl. tepidum (Frigaard and Bryant 2006).…”