The FMO protein

In this article I review the history of research on the Fenna-Matthews-Olson (FMO) protein with emphasis on my contributions. The FMO protein, which transfers energy from the chlorosome to the reaction center in green sulfur bacteria, was discovered in 1962 and shown to contain bacteriochlorophyll a. From the absorption and circular dichroism spectra, it was clear that there was an exciton interaction between the bacteriochlorophyll molecules. Low temperature spectra indicated a seven-fold exciton splitting of the Q(y) band. The FMO protein was crystallized in 1964, and the X-ray structure determined in 1979 by B. W. Matthews, R. E. Fenna, M. C. Bolognesi, M. F. Schmidt and J.M. Olson. The structure showed that the protein consisted of three subunits, each containing seven bacteriochlorophyll molecules. The optical spectra were satisfactorily simulated in 1997. In living cells the FMO protein is located between the chlorosome and the reaction centers with the C3 symmetry axis perpendicular to the membrane. The FMO protein may be related to PscA in the reaction center.