ABSTRACT.
Photosystem I is an electron transfer protein complex. Available Xray
crystal structures showed that electron transfer pathways consist of
two nearly symmetric branches of co-factors converging at the first iron
sulfur cluster FX, which is followed by two terminal iron sulfur clusters
FA and FB. In the present study, redox potentials of three iron sulfur
clusters in Photosystem I are calculated by means continuum electrostatic
methods. Structures of three clusters surrounded by ~ 10 A° nearby
amino acids, are extracted from the X-ray crystal structure for
Cyanobacterial photosystem I (PDB ID: 1JB0) and the midpoint
potentials Ems are determined by MCCE model. Our calculations show
that the first iron-sulfur cluster Fx has the lowest oxidation potential
among three iron-sulfur clusters, while FA is shown to has the highest
oxidation potential which agree with the experimental ordering