John Golbeck

The detailed molecular mechanisms of the bioassembly of the photosynthetic reaction centers are not well understood. What is known with certainty is that the last steps in the process include the assembly of the FX cluster, the binding of the stromal polypeptide PsaC (which contains the FA and FB clusters) and the subsequent binding of the stromal polypeptides PsaD and PsaE (Figure 2.2). The PsaC subunit, in turn, binds to the PS I core only when the FX, FA and FB clusters are present. Hence, the assembly of the Fe/S clusters is the key to the final steps in the binding of the stromal subunits. My students and I are taking two approaches to the bioassembly of Photosystem I. One involves the use of magnetic resonance spectroscopy to study the assembly of the stromal polypeptides PsaC, PsaD and PsaE. The other involves the use of molecular biology to study the assembly of the electron transfer cofactors, particularly the iron-sulfur clusters FX, FB and FA.