Structure of plant photosystem I revealed by theoretical modeling.

Photosystem (PS) I is a large membrane protein complex vital for oxygenic photosynthesis, one of the most important biological processes on the planet. We present an "atomic" model of higher plant PSI, based on theoretical modeling using the recent 4.4 angstroms x-ray crystal structure of PSI from pea. Because of the lack of information on the amino acid side chains in the x-ray structural model and the high cofactor content in this system, novel modeling techniques were developed. Our model reveals some important structural features of plant PSI that were not visible in the crystal structure, and our model sheds light on the evolutionary relationship between plant and cyanobacterial PSI.