• Prosthetic group features
• Fenna­Matthews­Olson (FMO) complex in SWISS­PROT/TREMBL
• FMO complex in alignment databases
• FMO complex in 3­D databases
• References

Centre	Bacteriochlorophyll	Metal coordination	Axial metal ligand	Formal metal oxidation states
1, 3, 4, 6	BChl­a	Pentacoordinate	NHis	MgII
2		Pentacoordinate	H2O
5		Pentacoordinate	OLeu
7		Pentacoordinate	NHis

Green sulphur bacteria (Chlorobiaceae) contain Fe-S type reaction centres and a large peripheral antenna complex called a chlorosome. The chlorosome collects light energy and transfers it to the membrane­bound reaction centre through the amphypathic Fenna­Matthews­Olson (FMO) complex, also known as bacteriochlorophyll a (BChl­a) protein [1].

The 3­D structures of the FMO complexes from Prosthecochloris aestuarii [2] and Chlorobium tepidum [3] have been determined. The complex consists of three identical subunits related by crystallographic three­fold symmetry. The monomer belongs to the mainly­ß class; a large ß­sheet consists of 17 strands and forms a shell which encloses seven BChl­a molecules (Figure 3BCL a). BChls 1-6 are arrayed as a skewed ring with BChl 7 roughly at the centre of the ring. BChls 3-7 are buried in the core of the monomer while BChls 1 and 2 are exposed on the surface of the monomer. All BChls are buried within the trimer complex, except for ring A of BChls 1 which is located on the surface of the trimer. The magnesium of each BChl­a is pentacoordinate although the fifth ligands vary: BChls 1, 3, 4, 6 and 7 are ligated by His residues, BChl 5 is coordinated to the backbone oxygen of Leu, while a bound water molecule serves as a ligand for BChl 2 (Figure 3BCL b).

The location of the FMO complex in the membrane remains unknown; a model has been proposed for the partially embedded FMO complex with the 3­fold axis perpendicular to the membrane plane [3].

FMO complex in SWISS­PROT/TREMBL

BCPA_CHLLI	Bacteriochlorophyll a protein (fragment); Chlorobium limicola
BCPA_CHLTE	Bacteriochlorophyll a protein; Chlorobium tepidum
BCPA_PROAE	Bacteriochlorophyll a protein; Prosthecochloris aestuarii

FMO complex in alignment databases

Protein Family	Pfam	LPFC 3­D alignment
27337; Bacteriochlorophyll a protein	-	-

PDB	MSD	scop	BSM	RELI Base	Header	¹
1ksa	1ksa	1ksa	1ksa	1ksa	Bacteriochlorophyll a protein; Chlorobium tepidum	-
4bcl	4bcl	3bcl	4bcl	4bcl	Bacteriochlorophyll a protein; Prosthecochloris aestuarii	-

¹ Macromolecular Structures abstract. Full text is available to BioMedNet Members

References

1. van Grondelle, R., Dekker, J.P., Gillbro, T. and Sundström, V. (1994) Energy transfer and trapping in photosynthesis. Biochim. Biophys. Acta 1187, 1-65.
2. Tronrud, D.E., Schmid, M.F. and Matthews, B.W. (1986) Structure and X­ray amino acid sequence of a bacteriochlorophyll a protein from Prosthecochloris aestuarii refined at 1.9 Å resolution. J. Mol. Biol. 188, 443-454.
3. Li, Y.­F., Zhou, W., Blankenship, R.E. and Allen, J.P. (1997) Crystal structure of the bacteriochlorophyll a protein from Chlorobium tepidum. J. Mol. Biol. 271, 456-471.

Bibliography on structural studies of Fenna­Matthews­Olson complex

ASU Photosynthesis Center